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feat: add BlendMath (colorkey match + ARGB unpack)

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Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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gamer147
2026-07-08 19:04:12 -04:00
parent 34cdfeda0e
commit 4ee7a26e3f
2 changed files with 56 additions and 0 deletions
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engine/Age.Engine/Model/BlendMath.cs Normal file
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namespace Age.Engine.Model;
/// <summary>Pure blend helpers shared by the engine resolution and the host blit. Colorkey semantics come
/// from the native loader (docs/engine-re.md §"Blend & transparency"): op arg 3 &lt; 0 = no key; otherwise
/// the operand is 0xRRGGBB and matching (R,G,B) texels are transparent (operand 0 = key black).</summary>
public static class BlendMath
{
/// <summary>A colorkey operand &gt;= 0 is an active key; a negative operand means "no colorkey".</summary>
public static bool HasColorKey(long colorKey) => colorKey >= 0;
/// <summary>True when (r,g,b) exactly equals the key's 0xRRGGBB bytes. Always false when there is no key.</summary>
public static bool ColorKeyMatches(byte r, byte g, byte b, long colorKey)
{
if (!HasColorKey(colorKey)) return false;
return r == ((colorKey >> 16) & 0xff) && g == ((colorKey >> 8) & 0xff) && b == (colorKey & 0xff);
}
/// <summary>Split a 0xAARRGGBB packed color (see GfxState.PackColor) into its byte channels.</summary>
public static (int A, int R, int G, int B) UnpackArgb(long packed)
=> ((int)((packed >> 24) & 0xff), (int)((packed >> 16) & 0xff),
(int)((packed >> 8) & 0xff), (int)(packed & 0xff));
}