asimage.html

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## libAfterImage/asimage.h

SYNOPSIS

     Defines main structures and function for image manipulation.

DESCRIPTION

     libAfterImage provides powerful functionality to load, store
     and transform images. It allows for smaller memory utilization by
     utilizing run-length encoding of the image data. There could be
     different levels of compression selected, allowing to choose best
     speed/memory ratio.

SEE ALSO

     Structures :
              ASImage
              ASImageManager
              ASImageBevel
              ASImageDecoder
              ASImageOutput
              ASImageLayer
              ASGradient

     Functions :
              asimage_init(), asimage_start(), create_asimage(),
              clone_asimage(), destroy_asimage()

       ImageManager Reference counting and managing :
              create_image_manager(), destroy_image_manager(),
              store_asimage(), fetch_asimage(), dup_asimage(),
              release_asimage(), release_asimage_by_name()

       Layers helper functions :
              init_image_layers(), create_image_layers(),
              destroy_image_layers()

       Encoding :
              asimage_add_line(),   asimage_add_line_mono(),
              asimage_print_line(), get_asimage_chanmask(),
              move_asimage_channel(), copy_asimage_channel(),
              copy_asimage_lines()

       Decoding
              start_image_decoding(), stop_image_decoding(),
              asimage_decode_line (), set_decoder_shift(),
              set_decoder_back_color()

       Output :
              start_image_output(), set_image_output_back_color(),
              toggle_image_output_direction(), stop_image_output()

     Other libAfterImage modules :
              ascmap.h asfont.h asimage.h asvisual.h blender.h export.h
              import.h transform.h ximage.h

AUTHOR

     Sasha Vasko <sasha at aftercode dot net>

## libAfterImage/ASImage

NAME

     ASImage

SYNOPSIS

     ASImage is main structure to hold image data.

DESCRIPTION

     Images are stored internally split into ARGB channels, each split
     into scanline. Each scanline is stored the following format to allow
     for RLE compression :
     component := <line><line>...<line>
     line      := <block><block>...<block><EOL>
     block     := <EOL>|<simple_block>|<long_block>|<direct_block>

     EOL       := 00000000 (all zero bits)

     simple_block  := <ctrl_byte1><value_byte>
     ctrl_byte1    := 00NNNNNN (first two bits are 0 remaining are length)

     long_block    := <ctrl_byte2><more_length_byte><value_byte>
     ctrl_byte2    := 01NNNNNN (NNNNNN are high 6 bits of length)
     more_length_byte := low 8 bits of length

     direct_block  := <ctrl_byte3><value_byte><value_byte>...<value_byte>
     ctrl_byte3    := [1NNNNNNN|11111111] (first bit is 1, remaining are
                        length. If it is all 1's - then remaining part of
                        the line up until image width is monolithic
                        uncompressed direct block)

SEE ALSO

      asimage_init()
      asimage_start()
      create_asimage()
      destroy_asimage()

SOURCE

        struct ASImageAlternative;
        struct ASImageManager;

        /* magic number identifying ASFont data structure */
        #define MAGIC_ASIMAGE            0xA3A314AE

## libAfterImage/LIMITS

NAME

     MAX_IMPORT_IMAGE_SIZE
     MAX_BEVEL_OUTLINE

FUNCTION

        MAX_IMPORT_IMAGE_SIZE   effectively limits size of the allowed
                                images to be loaded from files. That is
                                needed to be able to filter out corrupt files.

        MAX_BEVEL_OUTLINE       Limit on bevel outline to be drawn around
                                the image.

SOURCE

        #define MAX_IMPORT_IMAGE_SIZE   4000
        #define MAX_BEVEL_OUTLINE       100
        #define MAX_SEARCH_PATHS        8      /* prudently limiting ourselfs */

## libAfterImage/ASImageManager

NAME

     ASImageManager

DESCRIPTION

     Global data identifying connection to external libraries, as well as
     images location paths.
     This structure could be used to maintain repository of loaded images
     in order to avoid loading same image more then once.
     It holds hash of loaded image names.

SOURCE

        typedef struct ASImageManager
        {
            ASHashTable  *image_hash ;
            /* misc stuff that may come handy : */
            char         *search_path[MAX_SEARCH_PATHS+1];
            double        gamma ;
        }ASImageManager;

## libAfterImage/ASVectorPalette

NAME

     ASScientificPalette

DESCRIPTION

     Contains pallette allowing us to map double values in vector image
     data into actuall ARGB values.

SOURCE

        typedef struct ASVectorPalette
        {
            unsigned int npoints ;
            double *points ;
            CARD16 *channels[IC_NUM_CHANNELS] ;        /* ARGB data for key points. */
            ARGB32  default_color;
        }ASVectorPalette;

## libAfterImage/ASImageBevel

NAME

     ASImageBevel

SYNOPSIS

     ASImageBevel describes bevel to be drawn around the image.

DESCRIPTION

     Bevel is used to create 3D effect while drawing buttons, or any other
     image that needs to be framed. Bevel is drawn using 2 primary colors:
     one for top and left sides - hi color, and another for bottom and
     right sides - low color. There are additionally 3 auxiliary colors:
     hihi is used for the edge of top-left corner, hilo is used for the
     edge of top-right and bottom-left corners, and lolo is used for the
     edge of bottom-right corner. Colors are specified as ARGB and contain
     alpha component, thus allowing for semitransparent bevels.

     Bevel consists of outline and inline. Outline is drawn outside of the
     image boundaries and its size adds to image size as the result. Alpha
     component of the outline is constant. Inline is drawn on top of the
     image and its alpha component is fading towards the center of the
     image, thus creating illusion of smooth disappearing edge.

SOURCE

        typedef struct ASImageBevel
        {
        #define BEVEL_SOLID_INLINE  (0x01<<0)
            ASFlagType type ;                          /* reserved for future use */

            /* primary bevel colors */
            ARGB32      hi_color, lo_color ;

            /* these will be placed in the corners */
            ARGB32      hihi_color, hilo_color, lolo_color ;
            unsigned short left_outline, top_outline, right_outline, bottom_outline;
            unsigned short left_inline, top_inline, right_inline, bottom_inline;
        }ASImageBevel;

## libAfterImage/ASImageDecoder

NAME

     ASImageDecoder

SYNOPSIS

     ASImageDecoder describes the status of reading any particular ASImage,
     as well as providing detail on how it should be done.

DESCRIPTION

     ASImageDecoder works as an abstraction layer and as the way to
     automate several operations. Most of the transformations in
     libAfterImage are performed as operations on ASScanline data
     structure, that holds all or some of the channels of single image
     scanline. In order to automate data extraction from ASImage into
     ASScanline ASImageDecoder has been designed.

     It has following features :
     1) All missing scanlines, or channels of scanlines will be filled with
     supplied back_color
     2) It is possible to leave out some channels of the image, extracting
     only subset of channels. It is done by setting only needed flags in
     filter member.
     3) It is possible to extract sub-image of the image by setting offset_x
     and offset_y to top-left corner of sub-image, out_width - to width of
     the sub-image and calling decode_image_scanline method as many times
     as height of the sub-image.
     4) It is possible to apply bevel to extracted sub-image, by setting
     bevel member to specific ASImageBevel structure.

     Extracted Scanlines will be stored in buffer and it will be updated
     after each call to decode_image_scanline().

SOURCE

        typedef void (*decode_image_scanline_func)(struct ASImageDecoder *imdec);

        typedef struct ASImageDecoder
        {
            ASVisual       *asv;
            ASImage        *im ;
            ASFlagType      filter;      /* flags that mask set of channels to
                                          * be extracted from the image */

            ARGB32          back_color;  /* we fill missing scanlines with this
                                          * default - black*/
            unsigned int    offset_x,    /* left margin on source image before
                                          * which we skip everything */
                            out_width;   /* actual length of the output scanline */
            unsigned int    offset_y,    /* top margin */
                            out_height;
            ASImageBevel    *bevel;      /* bevel to wrap everything around with */

            /* offsets of the drawn bevel baseline on resulting image : */
            int            bevel_left, bevel_top, bevel_right, bevel_bottom ;

            /* scanline buffer containing current scanline */
            ASScanline      buffer;

            /* internal data : */
            unsigned short   bevel_h_addon, bevel_v_addon ;
            int             next_line ;
            decode_image_scanline_func decode_image_scanline ;
        }ASImageDecoder;

## libAfterImage/asimage/quality

FUNCTION

     Defines level of output quality/speed ratio

SOURCE

        #define ASIMAGE_QUALITY_DEFAULT -1
        #define ASIMAGE_QUALITY_POOR    0
        #define ASIMAGE_QUALITY_FAST    1
        #define ASIMAGE_QUALITY_GOOD    2
        #define ASIMAGE_QUALITY_TOP     3

        #define MAX_GRADIENT_DITHER_LINES   ASIMAGE_QUALITY_TOP+1

## libAfterImage/asimage/ASImageOutput

NAME

     ASImageOutput

SYNOPSIS

     ASImageOutput describes the output state of the transformation result.
     It is used to transparently write results into ASImage or XImage with
     different levels of quality.

DESCRIPTION

     libAfterImage allows for transformation result to be stored in both
     ASImage ( useful for long term storage and subsequent processing )
     and XImage ( useful for transfer of the result onto the X Server).
     At the same time there are 4 different quality levels of output
     implemented. They differ in the way special technics, like error
     diffusion and interpolation are applyed, and allow for fine grained
     selection of quality/speed ratio. ASIMAGE_QUALITY_GOOD should be good
     enough for most applications.
     The following additional output features are implemented :
     1) Filling of the missing channels with supplied values.
     2) Error diffusion to improve quality while converting from internal
          24.8 format to 8 bit format.
     3) Tiling of the output. If tiling_step is greater then 0, then each
          scanlines will be copied into lines found tiling_step one from
          another, upto the edge of the image.
     4) Reverse order of output. Output image will be mirrored along y
          axis if bottom_to_top is set to True.

NOTES

     The output_image_scanline method should be called for each scanline
     to be stored. Convenience functions listed below should be used to
     safely alter state of the output instead of direct manipulation of
     the data members. (makes you pity you don't write in C++ doesn't it ?)

     Also There is a trick in the way how output_image_scanline handles
     empty scanlines while writing ASImage. If back_color of empty scanline
     matches back_color of ASImageOutput - then particular line is erased!
     If back_colors are same - then particular line of ASImage gets filled
     with the back_color of ASScanline. First approach is usefull when
     resulting image will be used in subsequent call to merge_layers - in
     such case knowing back_color of image is good enough and we don't need
     to store lines with the same color. In case where ASImage will be
     converted into Pixmap/XImage - second approach is preferable, since
     that conversion does not take into consideration image's back color -
     we may want to change it in the future.

SEE ALSO

     start_image_output()
     set_image_output_back_color()
     toggle_image_output_direction()
     stop_image_output()

SOURCE

        typedef void (*encode_image_scanline_func)( struct ASImageOutput *imout,
                                                    ASScanline *to_store );
        typedef void (*output_image_scanline_func)( struct ASImageOutput *,
                                                    ASScanline *, int );

        typedef struct ASImageOutput
        {
            ASVisual        *asv;
            ASImage         *im ;
            ASAltImFormats   out_format ;
            CARD32           chan_fill[4];
            int              buffer_shift;  /* -1 means - buffer is empty,
                                             * 0 - no shift,
                                             * 8 - use 8 bit precision */
            int              next_line ;    /* next scanline to be written */
            unsigned int     tiling_step;   /* each line written will be repeated
                                             * with this step until we exceed
                                             * image size */
            unsigned int     tiling_range;  /* Limits region in which we need to
                                             * tile. If set to 0 then image height
                                             * is used */
            int              bottom_to_top; /* -1 if we should output in
                                             * bottom to top order, +1 otherwise*/

            int              quality ;      /* see above */

            output_image_scanline_func
                output_image_scanline ;  /* high level interface - division,
                                          * error diffusion as well as encoding */
            encode_image_scanline_func
                encode_image_scanline ;  /* low level interface - encoding only */

            /* internal data members : */
            ASScanline       buffer[2], *used, *available;
        }ASImageOutput;

## libAfterImage/asimage/ASImageLayer

NAME

     ASImageLayer

SYNOPSIS

     ASImageLayer specifies parameters of the image superimposition.

DESCRIPTION

     libAfterImage allows for simultaneous superimposition (overlaying) of
     arbitrary number of images. To facilitate this ASImageLayer structure
     has been created in order to specify parameters of each image
     participating in overlaying operation. Images need not to be exact
     same size. For each image its position on destination is specified
     via dst_x and dst_y data members. Each image maybe tiled and clipped
     to fit into rectangle specified by clip_x, clip_y, clip_width,
     clip_height ( in image coordinates - not destination ). If image is
     missing, then area specified by dst_x, dst_y, clip_width, clip_height
     will be filled with solid_color.
     Entire image will be tinted using tint parameter prior to overlaying.
     Bevel specified by bevel member will be drawn over image prior to
     overlaying. Specific overlay method has to be specified.
     merge_scanlines method is pointer to a function,
     that accepts 2 ASScanlines as arguments and performs overlaying of
     first one with the second one.
     There are 15 different merge_scanline methods implemented in
     libAfterImage, including alpha-blending, tinting, averaging,
     HSV and HSL colorspace operations, etc.

NOTES

     ASImageLayer s could be organized into chains using next pointers.
     Since there could be a need to rearrange layers and maybe bypass some
     layers - we need to provide for flexibility, while at the same time
     allowing for simplicity of arrays. As the result next pointers could
     be used to link together continuous arrays of layer, like so :
     array1: [layer1(next==NULL)][layer2(next!=NULL)]
              ____________________________|
              V
     array2: [layer3(next==NULL)][layer4(next==NULL)][layer5(next!=NULL)]
              ________________________________________________|
              V
     array3: [layer6(next==NULL)][layer7(next==layer7)]
                                    ^______|

     While iterating throught such a list we check for two conditions -
     exceeding count of layers and layer pointing to self. When any of
     that is met - we stopping iteration.

SEE ALSO

     merge_layers()
     blender.h

SOURCE

        typedef struct ASImageLayer
        {
            ASImage *im;
            ARGB32   solid_color ;                  /* If im == NULL, then fill
                                                     * the area with this color. */

            int dst_x, dst_y;                       /* placement in overall
                                                     * composition */

            /* clip area could be partially outside of the image -
             * image gets tiled in it */
            int clip_x, clip_y;
            unsigned int clip_width, clip_height;

            ARGB32 tint ;                           /* if 0 - no tint */
            ASImageBevel *bevel ;                   /* border to wrap layer with
                                                     * (for buttons, etc.)*/

            /* if image is clipped then we need to specify offsets of bevel as
             * related to clipped rectangle. Normally it should be :
             * 0, 0, im->width, im->height. And if width/height left 0 - it will
             * default to this values. Note that clipped image MUST be entirely
             * inside the bevel rectangle. !!!*/
            int bevel_x, bevel_y;
            unsigned int bevel_width, bevel_height;

            int merge_mode ;                        /* reserved for future use */
            merge_scanlines_func merge_scanlines ;  /* overlay method */
            struct ASImageLayer *next;              /* optional pointer to next
                                                     * layer. If it points to
                                                     * itself - then end of the
                                                     * chain.*/
            void *data;                             /* hook to hung data on */
        }ASImageLayer;

## libAfterImage/asimage/GRADIENT_TYPE_flags

FUNCTION

     Combination of this flags defines the way gradient is rendered.

SOURCE

        #define GRADIENT_TYPE_MASK          0x0003
        #define GRADIENT_TYPE_ORIENTATION   0x0002
        #define GRADIENT_TYPE_DIAG          0x0001

## libAfterImage/asimage/GRADIENT_TYPE

FUNCTION

     This are named combinations of above flags to define type of gradient.

SEE ALSO

     GRADIENT_TYPE_flags

SOURCE

        #define GRADIENT_Left2Right             0
        #define GRADIENT_TopLeft2BottomRight    GRADIENT_TYPE_DIAG
        #define GRADIENT_Top2Bottom             GRADIENT_TYPE_ORIENTATION
        #define GRADIENT_BottomLeft2TopRight    (GRADIENT_TYPE_DIAG| \
                                                 GRADIENT_TYPE_ORIENTATION)

## libAfterImage/ASGradient

NAME

     ASGradient

SYNOPSIS

     ASGradient describes how gradient is to be drawn.

DESCRIPTION

     libAfterImage includes functionality to draw multipoint gradients in
     4 different directions left->right, top->bottom and diagonal
     lefttop->rightbottom and bottomleft->topright. Each gradient described
     by type, number of colors (or anchor points), ARGB values for each
     color and offsets of each point from the beginning of gradient in
     fractions of entire length. There should be at least 2 anchor points.
     very first point should have offset of 0. and last point should have
     offset of 1. Gradients are drawn in ARGB colorspace, so it is possible
     to have semitransparent gradients.

SEE ALSO

     make_gradient()

SOURCE

        typedef struct ASGradient
        {
            int         type;       /* see GRADIENT_TYPE above */

            int         npoints;    /* number of anchor points */
            ARGB32     *color;      /* ARGB color values for each anchor point  */
            double     *offset;     /* offset of each point from the beginning in
                                     * fractions of entire length */
        }ASGradient;

## libAfterImage/asimage/flip

FUNCTION

     This are flags that define rotation angle.
     FLIP_VERTICAL defines rotation of 90 degrees counterclockwise.
     FLIP_UPSIDEDOWN defines rotation of 180 degrees counterclockwise.
     combined they define rotation of 270 degrees counterclockwise.

SOURCE

        #define FLIP_VERTICAL       (0x01<<0)
        #define FLIP_UPSIDEDOWN     (0x01<<1)
        #define FLIP_MASK           (FLIP_UPSIDEDOWN|FLIP_VERTICAL)

## libAfterImage/asimage/tint

FUNCTION

     We use 32 bit ARGB values to define how tinting should be done.
     The formula for tinting particular channel data goes like that:
     tinted_data = (image_data * tint)/128
     So if tint channel value is greater then 127 - same channel will be
     brighter in destination image; if it is lower then 127 - same channel
     will be darker in destination image. Tint channel value of 127
     ( or 0x7F hex ) does not change anything.
     Alpha channel is tinted as well, allowing for creation of
     semitransparent images. Calculations are performed in 24.8 format -
     with 8 bit precision. Result is saturated to avoid overflow, and
     precision is carried over to next pixel ( error diffusion ), when con
     verting 24.8 to 8 bit format.

SOURCE

        #define TINT_NONE           0
        #define TINT_LEAVE_SAME     (0x7F7F7F7F)
        #define TINT_HALF_DARKER    (0x3F3F3F3F)
        #define TINT_HALF_BRIGHTER  (0xCFCFCFCF)
        #define TINT_RED            (0x7F7F0000)
        #define TINT_GREEN          (0x7F007F00)
        #define TINT_BLUE           (0x7F00007F)

## libAfterImage/asimage/compression

FUNCTION

     Defines the level of compression to attempt on ASImage scanlines.
     valid values are in range of 0 to 100, with 100 being the highest
     compression.

SOURCE

        #define ASIM_COMPRESSION_NONE       0
        #define ASIM_COMPRESSION_FULL      100

## libAfterImage/asimage/asimage_init()

SYNOPSIS

     void asimage_init (ASImage * im, Bool free_resources);

INPUTS

     im             - pointer to valid ASImage structure
     free_resources - if True will make function attempt to free
                      all non-NULL pointers.

DESCRIPTION

        frees datamembers of the supplied ASImage structure, and
        initializes it to all 0.

## libAfterImage/asimage/asimage_start()

SYNOPSIS

     void asimage_start (ASImage * im, unsigned int width,
                                       unsigned int height,
                                       unsigned int compression);

INPUTS

     im          - pointer to valid ASImage structure
     width       - width of the image
     height      - height of the image
     compression - level of compression to perform on image data.
                   compression has to be in range of 0-100 with 100
                   signifying highest level of compression.

DESCRIPTION

     Allocates memory needed to store scanline of the image of supplied
     size. Assigns all the data members valid values. Makes sure that
     ASImage structure is ready to store image data.

NOTES

     In order to resize ASImage structure after asimage_start() has been
     called, asimage_init() must be invoked to free all the memory, and
     then asimage_start() has to be called with new dimensions.

## libAfterImage/asimage/create_asimage()

SYNOPSIS

     ASImage *create_asimage( unsigned int width,
                              unsigned int height,
                              unsigned int compression);

INPUTS

     width       - desired image width
     height      - desired image height
     compression - compression level in new ASImage( see asimage_start()
                   for more ).

RETURN VALUE

     Pointer to newly allocated and initialized ASImage structure on
     Success. NULL in case of any kind of error - that should never happen.

DESCRIPTION

     Performs memory allocation for the new ASImage structure, as well as
     initialization of allocated structure based on supplied parameters.

## libAfterImage/asimage/clone_asimage()

SYNOPSIS

     ASImage *clone_asimage(ASImage *src, ASFlagType filter );

INPUTS

     src      - original ASImage.
     filter   - bitmask of channels to be copied from one image to another.

RETURN VALUE

     New ASImage, as a copy of original image.

DESCRIPTION

     Creates exact clone of the original ASImage, with same compression,
     back_color and rest of the attributes. Only ASImage data will be
     carried over. Any attached alternative forms of images (XImages, etc.)
     will not be copied. Any channel with unset bit in filter will not be
     copied. Image name, ASImageManager and ref_count will not be copied -
     use store_asimage() afterwards and make sure you use different name,
     to avoid clashes with original image.

## libAfterImage/asimage/destroy_asimage()

SYNOPSIS

     void destroy_asimage( ASImage **im );

INPUTS

     im             - pointer to valid ASImage structure.

DESCRIPTION

     frees all the memory allocated for specified ASImage. If there was
     XImage attached to it - it will be deallocated as well.

EXAMPLE

     asview.c: ASView.5

## libAfterImage/asimage/destroy_asimage()

SYNOPSIS

     set_asimage_vector( ASImage *im, register double *vector );

INPUTS

     im             - pointer to valid ASImage structure.
     vector           - scientific data to attach to the image.

DESCRIPTION

     This function replaces contents of the vector member of ASImage
     structure with new double precision data. Data must have size
     of width*height ahere width and height are size of the ASImage.

## libAfterImage/asimage/ImageManager

DESCRIPTION

     create_image_manager()  - create ASImage management and reference
                               counting object.
     destroy_image_manager() - destroy management obejct.
     store_asimage()         - add ASImage to the refererence.
     fetch_asimage()         - retrieve previously stored image, incrementing
                               reference count.
     dup_asimage()           - increment reference count of stored ASImage.
     release_asimage()       - decrement reference count/destroy ASImage.
     release_asimage_by_name()

## libAfterImage/asimage/create_image_manager()

SYNOPSIS

     ASImageManager *create_image_manager( ASImageManager *reusable_memory,
                                           double gamma, ... );

INPUTS

     reusable_memory - optional pointer to a block of memory to be used to
                       store ASImageManager object.
     double gamma    - value of gamma correction to be used while loading
                       images from files.
     ...             - NULL terminated list of up to 8 PATH strings to list
                       locations at which images could be found.

DESCRIPTION

     Creates ASImageManager object in memory and initializes it with
     requested gamma value and PATH list. This Object will contain a hash
     table referencing all the loaded images. When such object is used while
     loading images from the file - gamma and PATH values will be used, so
     that all the loaded and referenced images will have same parameters.
     File name will be used as the image name, and if same file is attempted
     to be loaded again - instead reference will be incremented, and
     previously loaded image will be retyrned. All the images stored in
     ASImageManager's table will contain a back pointer to it, and they must
     be deallocated only by calling release_asimage(). destroy_asimage() will
     refuse to deallocate such an image.

## libAfterImage/asimage/destroy_image_manager()

SYNOPSIS

     void destroy_image_manager( struct ASImageManager *imman, Bool reusable );

INPUTS

     imman           - pointer to ASImageManager object to be deallocated
     reusable        - if True, then memory that holds object itself will
                       not be deallocated. Usefull when object is created
                       on stack.

DESCRIPTION

     Destroys all the referenced images, PATH values and if reusable is False,
     also deallocates object's memory.

## libAfterImage/asimage/store_asimage()

SYNOPSIS

     Bool store_asimage( ASImageManager* imageman, ASImage *im, const char *name );

INPUTS

     imageman        - pointer to valid ASImageManager object.
     im              - pointer to the image to be stored.
     name            - unique name of the image.

DESCRIPTION

     Adds specifyed image to the ASImageManager's list of referenced images.
     Stored ASImage could be deallocated only by release_asimage(), or when
     ASImageManager object itself is destroyed.

## libAfterImage/asimage/fetch_asimage()

SYNOPSIS

     ASImage *fetch_asimage( ASImageManager* imageman, const char *name );

INPUTS

     imageman        - pointer to valid ASImageManager object.
     name            - unique name of the image.

DESCRIPTION

     Looks for image with the name in ASImageManager's list and if found,
     it will increment reference count and return pointer to it.

## libAfterImage/asimage/dup_asimage()

SYNOPSIS

     ASImage *dup_asimage( ASImage* im );

INPUTS

     im              - pointer to already referenced image.

DESCRIPTION

     Increments reference count on the specifyed ASImage.

## libAfterImage/asimage/release_asimage()

SYNOPSIS

     int    release_asimage( ASImage *im );

INPUTS

     im              - pointer to already referenced image.

DESCRIPTION

     Decrements reference count on the ASImage object and destroys it if
     reference count is below zero.

## libAfterImage/asimage/release_asimage_by_name()

SYNOPSIS

     int release_asimage_by_name( ASImageManager *imman, char *name );

INPUTS

     imageman        - pointer to valid ASImageManager object.
     name            - unique name of the image.

DESCRIPTION

     Finds ASImage known by specified name in ASImageManager's list and
     then calls release_asimage() on that image.

## libAfterImage/asimage/Layers

DESCRIPTION

     init_image_layers()    - initialize set of ASImageLayer structures.
     create_image_layers()  - allocate and initialize set of ASImageLayer's.
     destroy_image_layers() - destroy set of ASImageLayer structures.

## libAfterImage/asimage/init_image_layers()

SYNOPSIS

     inline void init_image_layers( register ASImageLayer *l, int count );

INPUTS

     l              - pointer to valid ASImage structure.
     count          - number of elements to initialize.

DESCRIPTION

     Initializes array on ASImageLayer structures to sensible defaults.
     Basically - all zeros and merge_scanlines == alphablend_scanlines.

## libAfterImage/asimage/create_image_layers()

SYNOPSIS

     ASImageLayer *create_image_layers( int count );

INPUTS

     count       - number of ASImageLayer structures in allocated array.

RETURN VALUE

     Pointer to newly allocated and initialized array of ASImageLayer
     structures on Success. NULL in case of any kind of error - that
     should never happen.

DESCRIPTION

     Performs memory allocation for the new array of ASImageLayer
     structures, as well as initialization of allocated structure to
     sensible defaults - merge_func will be set to alphablend_scanlines.

## libAfterImage/asimage/destroy_image_layers()

SYNOPSIS

     void destroy_image_layers( register ASImageLayer *l,
                                int count,
                                Bool reusable );
     l              - pointer to pointer to valid array of ASImageLayer
                        structures.
     count            - number of structures in array.
     reusable         - if True - then array itself will not be deallocates -
                        which is usable when it was allocated on stack.

DESCRIPTION

     frees all the memory allocated for specified array of ASImageLayer s.
     If there was ASImage and/or ASImageBevel attached to it - it will be
     deallocated as well.

## libAfterImage/asimage/Encoding

DESCRIPTION

     asimage_add_line()       - encode raw scanline data
     asimage_add_line_mono()  - encode scanline to have all the same pixels
     get_asimage_chanmask()   - determine what channels contain data.
     asimage_print_line()     - print stored scanline to stderr.
     asimage_decode_line()    - decode single scanline of the ASImage
     move_asimage_channel()   - move channel's data from one image to another.
     copy_asimage_channel()   - duplicate channel's data from one image to
                                another.
     copy_asimage_lines()     - duplicate range of scanline from one image
                                to another.

## libAfterImage/asimage/asimage_add_line()

SYNOPSIS

     size_t asimage_add_line ( ASImage * im, ColorPart color,
                               CARD32 * data, unsigned int y);

INPUTS

     im      - pointer to valid ASImage structure
     color   - color channel's number
     data    - raw channel data of 32 bits per pixel - only lowest 8 bits
               gets encoded.
     y       - image row starting with 0

RETURN VALUE

     asimage_add_line() return size of the encoded channel scanline in
     bytes. On failure it will return 0.

DESCRIPTION

     Encodes raw data of the single channel into ASImage channel scanline.
     based on compression level selected for this ASImage all or part of
     the scanline will be RLE encoded.

## libAfterImage/asimage/asimage_add_line_mono()

SYNOPSIS

     size_t asimage_add_line_mono ( ASImage * im, ColorPart color,
                                    CARD8 value, unsigned int y);

INPUTS

     im             - pointer to valid ASImage structure
     color          - color channel's number
     value          - value for the channel
     y              - image row starting with 0

RETURN VALUE

     asimage_add_line_mono() return size of the encoded channel scanline
     in bytes. On failure it will return 0.

DESCRIPTION

     encodes ASImage channel scanline to have same color components
     value in every pixel. Useful for vertical gradients for example.

## libAfterImage/asimage/get_asimage_chanmask()

SYNOPSIS

     ASFlagType get_asimage_chanmask( ASImage *im);

INPUTS

     im         - valid ASImage object.

DESCRIPTION

     goes throu all the scanlines of the ASImage and toggles bits representing
     those components that have at least some data.

## libAfterImage/asimage/move_asimage_channel()

SYNOPSIS

     void move_asimage_channel( ASImage *dst, int channel_dst,
                                ASImage *src, int channel_src );

INPUTS

     dst         - ASImage which will have its channel substituted;
     channel_dst - what channel to move data to;
     src         - ASImage which will donate its channel to dst;
     channel_src - what source image channel to move data from.

DESCRIPTION

     MOves channel data from one ASImage to another, while discarding
     what was already in destination's channel.

NOTES

     Source image (donor) will loose its channel data, as it will be
     moved to destination ASImage. Also there is a condition that both
     images must be of the same width - otherwise function returns
     without doing anything. If height is different - the minimum of
     two will be used.

## libAfterImage/asimage/copy_asimage_channel()

SYNOPSIS

     void copy_asimage_channel( ASImage *dst, int channel_dst,
                                ASImage *src, int channel_src );

INPUTS

     dst         - ASImage which will have its channel substituted;
     channel_dst - what channel to copy data to;
     src         - ASImage which will donate its channel to dst;
     channel_src - what source image channel to copy data from.

DESCRIPTION

     Same as move_asimage_channel() but makes copy of channel's data
     instead of simply moving it from one image to another.

## libAfterImage/asimage/copy_asimage_lines()

SYNOPSIS

     void copy_asimage_lines( ASImage *dst, unsigned int offset_dst,
                              ASImage *src, unsigned int offset_src,
                              unsigned int nlines, ASFlagType filter );

INPUTS

     dst         - ASImage which will have its channel substituted;
     offset_dst  - scanline in destination image to copy to;
     src         - ASImage which will donate its channel to dst;
     offset_src  - scanline in source image to copy data from;
     nlines      - number of scanlines to be copied;
     filter      - specifies what channels should be copied.

DESCRIPTION

     Makes copy of scanline data for continuos set of scanlines, affecting
     only those channels marked in filter.
     NOTE
     Images must be of the same width.

## libAfterImage/asimage/verbosity

FUNCTION

     This are flags that define what should be printed by
     asimage_print_line():
        VRB_LINE_SUMMARY    - print only summary for each scanline
        VRB_LINE_CONTENT    - print summary and data for each scanline
        VRB_CTRL_EXPLAIN    - print summary, data and control codes for each
                              scanline

SOURCE

        #define VRB_LINE_SUMMARY    (0x01<<0)
        #define VRB_LINE_CONTENT    (0x01<<1)
        #define VRB_CTRL_EXPLAIN    (0x01<<2)
        #define VRB_EVERYTHING      (VRB_LINE_SUMMARY|VRB_CTRL_EXPLAIN| \
                                     VRB_LINE_CONTENT)

## libAfterImage/asimage/asimage_print_line()

SYNOPSIS

        unsigned int asimage_print_line ( ASImage * im, ColorPart color,
                                          unsigned int y,
                                          unsigned long verbosity);

INPUTS

     im             - pointer to valid ASImage structure
     color          - color channel's number
     y              - image row starting with 0
     verbosity      - verbosity level - any combination of flags is
                      allowed

RETURN VALUE

     amount of memory used by this particular channel of specified
     scanline.

DESCRIPTION

     asimage_print_line() prints data stored in specified image scanline
     channel. That may include simple summary of how much memory is used,
     actual visible data, and/or RLE control codes. That helps to see
     how effectively data is encoded.

     Useful mostly for debugging purposes.

## libAfterImage/asimage/Decoding

DESCRIPTION

     start_image_decoding()   - allocates and initializes decoder
                                structure.
     set_decoder_shift()      - changes the shift value of decoder - 8 or 0.
     set_decoder_back_color() - changes the back color to be used while
                                decoding the image.
     stop_image_decoding()    - finishes decoding, frees all allocated
                                memory.

## libAfterImage/asimage/start_image_decoding()

SYNOPSIS

     ASImageDecoder *start_image_decoding( ASVisual *asv,ASImage *im,
                                           ASFlagType filter,
                                           int offset_x, int offset_y,
                                           unsigned int out_width,
                                           unsigned int out_height,
                                           ASImageBevel *bevel );

INPUTS

     asv      - pointer to valid ASVisual structure ( needed mostly
                to see if we are in BGR mode or not );
     im       - ASImage we are going to decode;
     filter   - bitmask where set bits mark channels that has to be
                decoded.
     offset_x - left margin inside im, from which we should start
                reading pixel data, effectively clipping source image.
     offset_y - top margin inside im, from which we should start
                reading scanlines, effectively clipping source image.
                Note that when edge of the image is reached,
                subsequent requests for scanlines will wrap around to
                the top of the image, and not offset_y.
     out_width- width of the scanline needed. If it is larger then
                source image - then image data will be tiled in it.
                If it is smaller - then image data will be clipped.
     out_height - height of the output drawable. -1 means that same as
              image height. if out_height is greater then image height,
              then image will be tiled.
     bevel    - NULL or pointer to valid ASImageBevel structure if
                decoded data should be overlayed with bevel at the
                time of decoding.

RETURN VALUE

     start_image_decoding() returns pointer to newly allocated
     ASImageDecoder structure on success, NULL on failure.

DESCRIPTION

     Normal process of reading image data from ASImage consists of
     3 steps :
     1) start decoding by calling start_image_decoding.
     2) call decode_image_scanline() method of returned structure, for
     each scanline upto desired height of the target image. Decoded data
     will be returned in buffer member of the ASImageDecoder structure.
     3) finish decoding and deallocated all the used memory by calling
     stop_image_decoding()

## libAfterImage/asimage/set_decoder_bevel_geom()

SYNOPSIS

     void set_decoder_bevel_geom( ASImageDecoder *imdec, int x, int y,
                                  unsigned int width, unsigned int height );

INPUTS

     imdec   - pointer to pointer to structure, previously created
               by start_image_decoding.
     x,y     - left top position of the inner border of the Bevel outline
               as related to the origin of subimage being decoded.
     width,
     height  - widtha and height of the inner border of the bevel outline.

DESCRIPTION

     This function should be used to change default placement of the bevel
     on decoded image. For example if you only need to render small part of
     the button, that is being rendered from transparency image.
     NOTE
     This call modifies bevel_h_addon and bevel_v_addon of
     ASImageDecoder structure.

## libAfterImage/asimage/set_decoder_shift()

SYNOPSIS

     void set_decoder_shift( ASImageDecoder *imdec, int shift );

INPUTS

     imdec   - pointer to pointer to structure, previously created
                by start_image_decoding.
     shift   - new value to be used as the shift while decoding image.
               valid values are 8 and 0.

DESCRIPTION

     This function should be used instead of directly modifyeing value of
     shift memebr of ASImageDecoder structure.

## libAfterImage/asimage/set_decoder_back_color()

SYNOPSIS

     void set_decoder_back_color( ASImageDecoder *imdec, ARGB32 back_color );

INPUTS

     imdec      - pointer to pointer to structure, previously created
                  by start_image_decoding.
     back_color - ARGB32 color value to be used as the background color to
                  fill empty spaces in decoded ASImage.

DESCRIPTION

     This function should be used instead of directly modifyeing value of
     back_color memebr of ASImageDecoder structure.

## libAfterImage/asimage/stop_image_decoding()

SYNOPSIS

     void stop_image_decoding( ASImageDecoder **pimdec );

INPUTS

     pimdec   - pointer to pointer to structure, previously created
                by start_image_decoding.

RETURN VALUE

     pimdec - pointer to ASImageDecoder will be reset to NULL.

SEE ALSO

     start_image_decoding()

## libAfterImage/asimage/Output

DESCRIPTION

     start_image_output               - initializes output structure
     set_image_output_back_color      - changes background color of output
     toggle_image_output_direction    - reverses vertical direction of
                                        output
     stop_image_output                - finishes output, frees all the
                                        allocated memory.

## libAfterImage/asimage/start_image_output()

SYNOPSIS

     ASImageOutput *start_image_output ( struct ASVisual *asv,
                                         ASImage *im,
                                         ASAltImFormats format,
                                         int shift, int quality );

INPUTS

     asv      - pointer to valid ASVisual structure
     im       - destination ASImage
     format   - indicates that output should be written into alternative
                format, such as supplied XImage, ARGB32 array etc.
     shift    - precision of scanline data. Supported values are 0 - no
                precision, and 8 - 24.8 precision. Value of that argument
                defines by how much scanline data is shifted rightwards.
     quality  - what algorithms should be used while writing data out, i.e.
                full error diffusion, fast error diffusion, no error
                diffusion.

DESCRIPTION

     start_image_output() creates and initializes new ASImageOutput
     structure based on supplied parameters. Created structure can be
     subsequently used to write scanlines into destination image.
     It is effectively hiding differences of XImage and ASImage and other
     available output formats.
     outpt_image_scanline() method of the structure can be used to write
     out single scanline. Each written scanlines moves internal pointer to
     the next image line, and possibly writes several scanlines at once if
     tiling_step member is not 0.

## libAfterImage/asimage/set_image_output_back_color()

SYNOPSIS

     void set_image_output_back_color ( ASImageOutput *imout,
                                        ARGB32 back_color );

INPUTS

     imout      - ASImageOutput structure, previously created with
                  start_image_output();
     back_color - new background color value in ARGB format. This color
                  will be used to fill empty parts of outgoing scanlines.

## libAfterImage/asimage/toggle_image_output_direction()

SYNOPSIS

     void toggle_image_output_direction( ASImageOutput *imout );

INPUTS

     imout      - ASImageOutput structure, previously created with
                  start_image_output();

DESCRIPTION

     reverses vertical direction output. If previously scanlines has
     been written from top to bottom, for example, after this function is
     called they will be written in opposite direction. Current line does
     not change, unless it points to the very first or the very last
     image line. In this last case it will be moved to the opposing end of
     the image.

## libAfterImage/asimage/stop_image_output()

SYNOPSIS

     void stop_image_output( ASImageOutput **pimout );

INPUTS

     pimout     - pointer to pointer to ASImageOutput structure,
                  previously created with call to   start_image_output().

RETURN VALUE

     pimout     - pointer to ASImageOutput will be reset to NULL.

DESCRIPTION

     Completes image output process. Flushes all the internal buffers.
     Deallocates all the allocated memory. Resets pointer to NULL to
     avoid dereferencing invalid pointers.