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Initial handling of interlaced GIFs

This commit is contained in:
Jarrod Doyle 2024-09-06 18:55:34 +01:00
parent 3e4230e46f
commit a9a16f88e9
Signed by: Jayrude
GPG Key ID: 38B57B16E7C0ADF7
1 changed files with 59 additions and 7 deletions
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66
project/code/Images/GifDecoder.cs
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@ -86,6 +86,7 @@ public class GifDecoder
private byte[] _colors; private byte[] _colors;
private byte[] _pixelIndices; private byte[] _pixelIndices;
private int _transparentIndex; private int _transparentIndex;
private readonly bool _interlaced;
public ImageData(BinaryReader reader, byte[] globalColors, int transparentIndex) public ImageData(BinaryReader reader, byte[] globalColors, int transparentIndex)
{ {
@ -95,7 +96,7 @@ public class GifDecoder
var height = reader.ReadUInt16(); var height = reader.ReadUInt16();
var flags = reader.ReadByte(); var flags = reader.ReadByte();
var hasLocalColorTable = ((flags >> 7) & 0x1) != 0; var hasLocalColorTable = ((flags >> 7) & 0x1) != 0;
var interlaced = ((flags >> 6) & 0x1) != 0; // See appendix E for interlacing _interlaced = ((flags >> 6) & 0x1) != 0; // See appendix E for interlacing
var isLocalColorTableSorted = ((flags >> 5) & 0x1) != 0; var isLocalColorTableSorted = ((flags >> 5) & 0x1) != 0;
var sizeOfLocalColorTable = (byte)Math.Pow(2, (flags & 0x7) + 1); var sizeOfLocalColorTable = (byte)Math.Pow(2, (flags & 0x7) + 1);
byte[] colors; byte[] colors;
@ -256,14 +257,65 @@ public class GifDecoder
{ {
var bytesIdx = 0; var bytesIdx = 0;
var bytes = new byte[Width * Height * 4]; var bytes = new byte[Width * Height * 4];
void WritePixelBytes(int bytesOffset, int colorIndex)
{
bytes[bytesOffset] = _colors[colorIndex * 3];
bytes[bytesOffset + 1] = _colors[colorIndex * 3 + 1];
bytes[bytesOffset + 2] = _colors[colorIndex * 3 + 2];
// Fuck you LGS hardcoding the transparent index suck my balls
// bytes[bytesOffset++] = (byte)((colorIndex == _transparentIndex) ? 0 : 255);
bytes[bytesOffset + 3] = (byte)((colorIndex == 0) ? 0 : 255);
}
if (!_interlaced)
{
foreach (var colorIndex in _pixelIndices) foreach (var colorIndex in _pixelIndices)
{ {
bytes[bytesIdx++] = _colors[colorIndex * 3]; WritePixelBytes(bytesIdx, colorIndex);
bytes[bytesIdx++] = _colors[colorIndex * 3 + 1]; bytesIdx += 4;
bytes[bytesIdx++] = _colors[colorIndex * 3 + 2]; }
// Fuck you LGS hardcoding the transparent index suck my balls return bytes;
// bytes[bytesIdx++] = (byte)((colorIndex == _transparentIndex) ? 0 : 255); }
bytes[bytesIdx++] = (byte)((colorIndex == 0) ? 0 : 255);
var pass1Count = (int)Math.Ceiling(Height / 8.0f);
var pass2Count = (int)Math.Ceiling((Height - 4) / 8.0f);
var pass3Count = (int)Math.Ceiling((Height - 2) / 4.0f);
var pass4Count = (int)Math.Ceiling((Height - 1) / 2.0f);
var indicesOffset = 0;
var bytesPerRow = Width * 4;
for (var i = 0; i < pass1Count; i++)
{
bytesIdx = 8 * i * bytesPerRow;
for (var x = 0; x < Width; x++)
{
WritePixelBytes(bytesIdx + x * 4, _pixelIndices[indicesOffset++]);
}
}
for (var i = 0; i < pass2Count; i++)
{
bytesIdx = (4 + 8 * i) * bytesPerRow;
for (var x = 0; x < Width; x++)
{
WritePixelBytes(bytesIdx + x * 4, _pixelIndices[indicesOffset++]);
}
}
for (var i = 0; i < pass3Count; i++)
{
bytesIdx = (2 + 4 * i) * bytesPerRow;
for (var x = 0; x < Width; x++)
{
WritePixelBytes(bytesIdx + x * 4, _pixelIndices[indicesOffset++]);
}
}
for (var i = 0; i < pass4Count; i++)
{
bytesIdx = (1 + 2 * i) * bytesPerRow;
for (var x = 0; x < Width; x++)
{
WritePixelBytes(bytesIdx + x * 4, _pixelIndices[indicesOffset++]);
}
} }
return bytes; return bytes;
} }