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Fix rendering regression with TGA type 1 files with BGRA8 color (#15402)

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TGA uses BGR(A)8, stored in memory in that order. Irrlicht typically expects 0xAARRGGBB, which depends on endianness.
(This means that on little endian, no [B][G][R][A] -> 0xAARRGGBB conversion needs to be done, but Irrlicht was swapping the bytes.)

This makes both conversion functions consistently convert from [B][G][R]([A]) to 0xAARRGGBB (SColor), documents them properly and moves them to CImageLoaderTGA.cpp
so no poor soul shall be fooled by them in the near future.

---------

Co-authored-by: Ælla Chiana Moskopp <erle@dieweltistgarnichtso.net>
This commit is contained in:
Lars Müller 2024-11-19 13:37:05 +01:00 • committed by GitHub
parent 138052adfc
commit 15e8f9e6a0
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4 changed files with 32 additions and 33 deletions
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23
irr/src/CImageLoaderTGA.cpp
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@ -93,6 +93,25 @@ bool CImageLoaderTGA::isALoadableFileFormat(io::IReadFile *file) const
return (!strcmp(footer.Signature, "TRUEVISION-XFILE.")); // very old tgas are refused.
}
/// Converts *byte order* BGR to *endianness order* ARGB (SColor "=" u32)
static void convert_BGR8_to_SColor(const u8 *src, u32 n, u32 *dst)
{
for (u32 i = 0; i < n; ++i) {
const u8 *bgr = &src[3 * i];
dst[i] = 0xff000000 | (bgr[2] << 16) | (bgr[1] << 8) | bgr[0];
}
}
/// Converts *byte order* BGRA to *endianness order* ARGB (SColor "=" u32)
/// Note: This just copies from src to dst on little endian.
static void convert_BGRA8_to_SColor(const u8 *src, u32 n, u32 *dst)
{
for (u32 i = 0; i < n; ++i) {
const u8 *bgra = &src[4 * i];
dst[i] = (bgra[3] << 24) | (bgra[2] << 16) | (bgra[1] << 8) | bgra[0];
}
}
//! creates a surface from the file
IImage *CImageLoaderTGA::loadImage(io::IReadFile *file) const
{
@ -139,10 +158,10 @@ IImage *CImageLoaderTGA::loadImage(io::IReadFile *file) const
CColorConverter::convert_A1R5G5B5toA8R8G8B8(colorMap, header.ColorMapLength, palette);
break;
case 24:
CColorConverter::convert_B8G8R8toA8R8G8B8(colorMap, header.ColorMapLength, palette);
convert_BGR8_to_SColor(colorMap, header.ColorMapLength, palette);
break;
case 32:
CColorConverter::convert_B8G8R8A8toA8R8G8B8(colorMap, header.ColorMapLength, palette);
convert_BGRA8_to_SColor(colorMap, header.ColorMapLength, palette);
break;
}
delete[] colorMap;