Function determine_image_components

Source/astcenccli_image.cpp:115–194

See header for documentation. */

/* See header for documentation. */
unsigned int determine_image_components(
	const astcenc_image * img
) {
	unsigned int dim_x = img->dim_x;
	unsigned int dim_y = img->dim_y;
	unsigned int dim_z = img->dim_z;

	// Scan through the image data to determine how many color components the image has
	bool is_luma = true;
	bool has_alpha = false;

	if (img->data_type == ASTCENC_TYPE_U8)
	{
		for (unsigned int z = 0; z < dim_z; z++)
		{
			uint8_t* data8 = static_cast<uint8_t*>(img->data[z]);

			for (unsigned int y = 0; y < dim_y; y++)
			{
				for (unsigned int x = 0; x < dim_x; x++)
				{
					int r = data8[(4 * dim_x * y) + (4 * x    )];
					int g = data8[(4 * dim_x * y) + (4 * x + 1)];
					int b = data8[(4 * dim_x * y) + (4 * x + 2)];
					int a = data8[(4 * dim_x * y) + (4 * x + 3)];

					is_luma = is_luma && (r == g) && (r == b);
					has_alpha = has_alpha || (a != 0xFF);
				}
			}
		}
	}
	else if (img->data_type == ASTCENC_TYPE_F16)
	{
		for (unsigned int z = 0; z < dim_z; z++)
		{
			uint16_t* data16 = static_cast<uint16_t*>(img->data[z]);

			for (unsigned int y = 0; y < dim_y; y++)
			{
				for (unsigned int x = 0; x < dim_x; x++)
				{
					int r = data16[(4 * dim_x * y) + (4 * x    )];
					int g = data16[(4 * dim_x * y) + (4 * x + 1)];
					int b = data16[(4 * dim_x * y) + (4 * x + 2)];
					int a = data16[(4 * dim_x * y) + (4 * x + 3)];

					is_luma = is_luma && (r == g) && (r == b);
					has_alpha = has_alpha || ((a ^ 0xC3FF) != 0xFFFF);
					// a ^ 0xC3FF returns FFFF if and only if the input is 1.0
				}
			}
		}
	}
	else // if (img->data_type == ASTCENC_TYPE_F32)
	{
		assert(img->data_type == ASTCENC_TYPE_F32);