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using System; |
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|
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namespace Oni.Imaging |
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{ |
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internal static class Dxt1 |
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{ |
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public static Surface Decompress(Surface src, SurfaceFormat dstFormat) |
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{ |
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var dst = new Surface(src.Width, src.Height, dstFormat); |
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var colors = new Color[4]; |
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int srcOffset = 0; |
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|
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for (int y = 0; y < dst.Height; y += 4) |
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{ |
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for (int x = 0; x < dst.Width; x += 4) |
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{ |
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colors[0] = Color.ReadBgr565(src.Data, srcOffset); |
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srcOffset += 2; |
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|
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colors[1] = Color.ReadBgr565(src.Data, srcOffset); |
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srcOffset += 2; |
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|
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if (colors[0].ToBgr565() > colors[1].ToBgr565()) |
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{ |
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colors[2] = Color.Lerp(colors[0], colors[1], 1.0f / 3.0f); |
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colors[3] = Color.Lerp(colors[0], colors[1], 2.0f / 3.0f); |
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} |
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else |
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{ |
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colors[2] = Color.Lerp(colors[0], colors[1], 0.5f); |
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colors[3] = Color.Transparent; |
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} |
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|
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for (int y2 = 0; y2 < 4; y2++) |
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{ |
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int packedLookup = src.Data[srcOffset++]; |
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|
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for (int x2 = 0; x2 < 4; x2++) |
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{ |
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dst[x + x2, y + y2] = colors[packedLookup & 3]; |
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packedLookup >>= 2; |
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} |
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} |
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} |
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} |
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|
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return dst; |
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} |
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|
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public static Surface Compress(Surface src) |
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{ |
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var dst = new Surface(Utils.Align4(src.Width), Utils.Align4(src.Height), SurfaceFormat.DXT1); |
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|
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var block = new Vector3[16]; |
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var colors = new Vector3[4]; |
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var lookup = new int[16]; |
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int dstOffset = 0; |
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int height = dst.Height; |
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int width = dst.Width; |
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|
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for (int y = 0; y < height; y += 4) |
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{ |
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for (int x = 0; x < width; x += 4) |
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{ |
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for (int by = 0; by < 4; by++) |
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{ |
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for (int bx = 0; bx < 4; bx++) |
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block[by * 4 + bx] = src[x + bx, y + by].ToVector3(); |
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} |
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|
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CompressBlock(block, lookup, colors); |
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|
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Color.WriteBgr565(new Color(colors[0]), dst.Data, dstOffset); |
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dstOffset += 2; |
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|
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Color.WriteBgr565(new Color(colors[1]), dst.Data, dstOffset); |
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dstOffset += 2; |
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|
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for (int by = 0; by < 4; by++) |
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{ |
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int packedLookup = 0; |
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|
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for (int bx = 3; bx >= 0; bx--) |
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packedLookup = (packedLookup << 2) | lookup[by * 4 + bx]; |
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|
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dst.Data[dstOffset++] = (byte)packedLookup; |
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} |
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} |
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} |
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|
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return dst; |
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} |
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|
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private static void CompressBlock(Vector3[] block, int[] lookup, Vector3[] colors) |
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{ |
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colors[0] = block[0]; |
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colors[1] = block[0]; |
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|
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for (int i = 1; i < block.Length; i++) |
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{ |
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colors[0] = Vector3.Min(colors[0], block[i]); |
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colors[1] = Vector3.Max(colors[1], block[i]); |
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} |
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|
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int maxColor; |
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|
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if (new Color(colors[0]).ToBgr565() > new Color(colors[1]).ToBgr565()) |
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{ |
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colors[2] = Vector3.Lerp(colors[0], colors[1], 1.0f / 3.0f); |
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colors[3] = Vector3.Lerp(colors[0], colors[1], 2.0f / 3.0f); |
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maxColor = 4; |
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} |
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else |
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{ |
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colors[2] = Vector3.Lerp(colors[0], colors[1], 0.5f); |
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maxColor = 3; |
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} |
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|
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for (int i = 0; i < block.Length; i++) |
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{ |
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lookup[i] = LookupNearest(colors, block[i], maxColor); |
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} |
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} |
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|
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private static int LookupNearest(Vector3[] colors, Vector3 pixel, int maxColor) |
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{ |
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int index = 0; |
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float ds = Vector3.DistanceSquared(pixel, colors[0]); |
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|
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for (int i = 1; i < maxColor; i++) |
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{ |
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float newDs = Vector3.DistanceSquared(pixel, colors[i]); |
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|
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if (newDs < ds) |
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{ |
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ds = newDs; |
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index = i; |
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} |
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} |
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|
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return index; |
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} |
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} |
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} |
