How to load HDR file texture for Metal iOS & Mac?

Question

For OpenGL, we can simply use stb_image. Maybe, it also work for Metal with some extra work.

I don't want include more libs. So I tried MTKTextureLoader, but it didn't work with error.

MTKTextureLoaderErrorKey=Image decoding failed

What is the correct way to use HDR texture file with Metal API?

Answer 1

Since nobody is answering this question, I will post me solution below.

MTKTextureLoader *loader = [[MTKTextureLoader alloc] initWithDevice: _device];
        
NSDictionary *textureLoaderOptions = @ {
            MTKTextureLoaderOptionSRGB: @NO,
            MTKTextureLoaderOptionAllocateMipmaps: @YES,
            MTKTextureLoaderOptionGenerateMipmaps: @YES,
            MTKTextureLoaderOptionTextureUsage : @(MTLTextureUsageShaderRead),
            MTKTextureLoaderOptionTextureStorageMode : @(MTLStorageModePrivate),
            MTKTextureLoaderOptionOrigin: MTKTextureLoaderOriginFlippedVertically };

let pathHDR = [NSBundle.mainBundle pathForResource:@"filename" ofType:@"hdr"];

#if TARGET_OS_OSX
    let urlHDR = [[NSURL alloc] initFileURLWithPath:pathHDR];
    let imageData = [[[NSImage alloc] initWithContentsOfURL:urlHDR] TIFFRepresentation];
#else
    //let imageData = [[NSData alloc] initWithContentsOfFile:pathHDR];
    let image = [[UIImage alloc] initWithContentsOfFile:pathHDR];
    let imageData = UIImageJPEGRepresentation(image, 1.0);
    //UIImagePNGRepresentation(image);
#endif

_textureHDR = [loader newTextureWithData:imageData options:textureLoaderOptions error:&ERROR];