imencdec - encoding/decoding ASImage data from/to usable data structures libAfterImage/imencdec.h

       Sasha Vasko <sasha at aftercode dot net>
       libAfterImage/ASImageBevel

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

3rd Berkeley Distribution                      AfterStep v.2.2.12                                   imencdec(3x)

       Defines level of output quality/speed ratio

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

imencdec - encoding/decoding ASImage data from/to usable data structures libAfterImage/imencdec.h

       there  will  be no dithering and interpolation used while transforming ASIMAGE_QUALITY_FAST there will be
       no dithering and used while transforming but interpolation will be used.  ASIMAGE_QUALITY_GOOD simplified
       dithering  is  performed  in  addition  to  interpolation.   ASIMAGE_QUALITY_TOP   full   dithering   and
       interpolation.    ASIMAGE_QUALITY_DEFAULT   requests   current   default  setting  -  typically  same  as
       ASIMAGE_QUALITY_GOOD.  MAX_GRADIENT_DITHER_LINES defines number of lines  to  use  for  dithering,  while
       rendering  gradients,  in  order  to  create smooth effect. Higher number will slow things down, but will
       create better gradients.

       describes bevel to be drawn around the image.

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

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

       defines main structures and function for image storing, extraction and conversion to/from usable formats.

       - changes the back color to be used while decoding the image.

       - changes default placement of the bevel on decoded image.

       - changes the shift value of decoder - 8 or 0.

       - changes background color of output

       - allocates and initializes decoder structure.

       - initializes output structure

       - finishes decoding, frees all allocated memory.

       - finishes output, frees all the allocated memory.

       - reverses vertical direction of output

       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 useful 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.

       pimout      - pointer to ASImageOutput will be reset to NULL.

       start_image_decoding()
       libAfterImage/asimage/start_image_output()

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

           typedef struct ASImageOutput {
               struct ASVisual         *asv;
               struct 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 : */
               struct ASScanline        buffer[2], *used, *available; }ASImageOutput;

       libAfterImage/asimage/start_image_decoding()

       void stop_image_output( ASImageOutput **pimout );