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

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<doc>
  <title>Windows Bitmap File Format</title>
  <chapter>
    <title>Windows Bitmap File Format</title>
    <par>
      Windows bitmap files are stored in a device-independent bitmap (DIB)
      format
      that allows Windows to display the bitmap on any type of display device. The
      term "device independent" means that the bitmap specifies pixel color in a
      form independent of the method used by a display to represent color.
      Bitmaps can store 1, 4 and 8 bit indexed images and 16, 24
      and 32 RGB images. 4 and 8 bit images can also be compressed with RLE.
      Imaging can also read OS/2 bitmaps but can not save them.
    </par>

    <table>
      <title>Windows Bitmap File Format Support</title>
      <row>
        <th>Format</th>
        <th>TImageFormat equivalent</th>
        <th>Loading</th>
        <th>Saving</th>
      </row>
      <row>
        <td>1 bit indexed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>No</td>
      </row>
      <row>
        <td>4 bit indexed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>No</td>
      </row>
      <row>
        <td>8 bit indexed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>4 bit indexed RLE compressed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>No</td>
      </row>
      <row>
        <td>8 bit indexed RLE compressed</td>
        <td><icode>ifIndex8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>16 bit 555 RGB</td>
        <td><icode>ifX1R5G5B5</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>16 bit 565 RGB (note 1)</td>
        <td><icode>ifR5G6B5</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>16 bit 444 RGB (note 1)</td>
        <td><icode>ifX4R4G4B4</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>24 bit RGB</td>
        <td><icode>ifR8G8B8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>32 bit RGB</td>
        <td><icode>ifX8R8G8B8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>16 bit 1555 ARGB (note 2)</td>
        <td><icode>ifA1R5G5B5</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>16 bit 4444 ARGB (note 2)</td>
        <td><icode>ifA4R4G4B4</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
      <row>
        <td>32 bit ARGB (note 2)</td>
        <td><icode>ifA8R8G8B8</icode></td>
        <td>Yes</td><td>Yes</td>
      </row>
    </table>

    <note>
      1) Many image viewers and image editing programs do not support
      these 16 bit formats and treat them as X1R5G5B5 format.<br/>
      2) Alpha channels in BMP files are often ignored by some (many) viewers/editors.
    </note>

    <par>
      When working with Bitmap files you can find useful some options
      which can be set by <ref>SetOption</ref> function and their current values
      can be get by <ref>GetOption</ref> function.
      Or you can set them by modifying properties of <ref>TBitmapFileFormat</ref>
      class.
    </par>
    <table>
      <title>Options Related to Bitmap Files</title>
      <row>
        <th>OptionId</th>
        <th>Allowed Values</th>
        <th>Usage</th>
      </row>
      <row>
        <td><ref>ImagingBitmapRLE</ref></td>
        <td><b>0 (false)</b> or <b>1 (true)</b></td>
        <td>Indicates whether 8 bit Bitmap images will be saved with or without
        RLE compression (efficient only for images
        with large areas of the same color).
        Default value is <b>1 (true)</b>. </td>
      </row>
    </table>

  </chapter>
</doc>