Function IwiReadImage

DevIL/src-IL/src/il_iwi.cpp:288–398

ILboolean IwiReadImage(ILimage *BaseImage, IWIHEAD *Header, ILuint NumMips)
{
	ILimage	*Image;
	ILuint	SizeOfData;
	ILubyte	*CompData = NULL;
	ILint	i, j, k, m;

	for (i = NumMips; i >= 0; i--) {
		Image = BaseImage;
		// Go to the ith mipmap level.
		//  The mipmaps go from smallest to the largest.
		for (j = 0; j < i; j++)
			Image = Image->Mipmaps;

		switch (Header->Format)
		{
			case IWI_ARGB8: // These are all
			case IWI_RGB8:  //  uncompressed data,
			case IWI_A8:    //  so just read it.
				if (iread(Image->Data, 1, Image->SizeOfData) != Image->SizeOfData)
					return IL_FALSE;
				break;

			case IWI_ARGB4:  //@TODO: Find some test images for this.
				// Data is in ARGB4 format - 4 bits per component.
				SizeOfData = Image->Width * Image->Height * 2;
				CompData = (ILubyte*)ialloc(SizeOfData);  // Not really compressed - just in ARGB4 format.
				if (CompData == NULL)
					return IL_FALSE;
				if (iread(CompData, 1, SizeOfData) != SizeOfData) {
					ifree(CompData);
					return IL_FALSE;
				}
				for (k = 0, m = 0; k < (ILint)Image->SizeOfData; k += 4, m += 2) {
					// @TODO: Double the image data into the low and high nibbles for a better range of values.
					Image->Data[k+0] = CompData[m] & 0xF0;
					Image->Data[k+1] = (CompData[m] & 0x0F) << 4;
					Image->Data[k+2] = CompData[m+1] & 0xF0;
					Image->Data[k+3] = (CompData[m+1] & 0x0F) << 4;
				}
				break;

			case IWI_DXT1:
				// DXT1 data has at least 8 bytes, even for one pixel.
				SizeOfData = IL_MAX(Image->Width * Image->Height / 2, 8);
				CompData = (ILubyte*)ialloc(SizeOfData);  // Gives a 6:1 compression ratio (or 8:1 for DXT1 with alpha)
				if (CompData == NULL)
					return IL_FALSE;
				if (iread(CompData, 1, SizeOfData) != SizeOfData) {
					ifree(CompData);
					return IL_FALSE;
				}

				// Decompress the DXT1 data into Image (ith mipmap).
				if (!DecompressDXT1(Image, CompData)) {
					ifree(CompData);
					return IL_FALSE;
				}