galfar.imaginglib/Doc/VampyreDoc/FileFormats/Gif.xml

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<doc>
  <title>Graphics Interchange Format</title>
  <chapter>
    <title>Graphics Interchange Format</title>
    <par>
      GIF was
      (and is still used) popular format for storing images supporting
      multiple images per file and single color transparency.
      Pixel format is 8 bit indexed where each image frame can have
      its own color palette. GIF uses lossless LZW compression
      (patent expired few years ago).
      Imaging can load and save all GIFs with all frames and supports
      transparency.
    </par>
    
    <par>
      Loadng of animated GIFs was rewritten in Imaging 0.26.2 (based 
      on ExtraGIF mod by Sergey Galezdinov).
      It now supports two modes of operation: 
      <blist>
        <li><b>Raw Frames</b> just extracts raw frames from GIF files
          without any modification. Useful when you want to do your own
          GIF animator. Extracted frames are all in <icode>ifIndex8</icode>.
        </li>
        <li><b>Animated Frames</b> animates all frames using disposal methods
          and placement of frames onto logical screen. Correctly animates 
          all tested GIFs (several thousand). Animated frames are 
          in <icode>ifA8R8G8B8</icode> format so even rare true color GIFs 
          are supported (each frame has only 256 colors but you can place them
          side by side onto logical screen to create one larger true color image). 
          This is the default mode.  
        </li>        
      </blist> 
    </par>
    
    <par>
      You can select which mode you wan to use 
      with <ref>ImagingGIFLoadAnimated</ref> option along with   
      <ref>SetOption</ref> and <ref>GetOption</ref> functions.
      Or you can set them by modifying properties of <ref>TGIFFileFormat</ref>
      class.
    </par> 
    
    <table>
      <title>Options Related to GIF Files</title>
      <row>
        <th>OptionId</th>
        <th>Allowed Values</th>
        <th>Usage</th>
      </row>
      <row>
        <td><ref>ImagingGIFLoadAnimated</ref></td>
        <td><b>0 (false)</b> or <b>1 (true)</b></td>
        <td>Boolean option that specifies whether GIF images with more frames
            are animated by Imaging (according to frame disposal methods) or just
            raw frames are loaded and sent to user (if you want to animate GIF yourself).
            Default value is <b>1 (true)</b>. </td>
      </row>
    </table>
    
    <table>
      <title>GIF File Format Support</title>
      <row>
        <th>Format</th>
        <th>TImageFormat equivalent</th>
        <th>Loading</th>
        <th>Saving</th>
      </row>
      <row>
        <td>up to 256 colors indexed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>true color with transparency for animated frames</td>
        <td><icode>ifA8R8G8B8</icode></td>
        <td>Yes</td><td>No</td>
      </row>
    </table>
       
    
  </chapter>
</doc>