How to use MTKTextureLoader to load png data

I am trying to load some PNG data with MTKTextureLoader newTextureWithData，but the result shows wrong at the alpha area.

Here is the code. I have an image URL, after it downloads successfully, I try to use the data or UIImagePNGRepresentation (image), they all show wrong.

    UIImage *tempImg = [UIImage imageWithData:data];
    CGImageRef cgRef = tempImg.CGImage;
    
    MTKTextureLoader *loader = [[MTKTextureLoader alloc] initWithDevice:device];
    id<MTLTexture> temp1 = [loader newTextureWithData:data options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil];
    NSData *tempData = UIImagePNGRepresentation(tempImg);
    id<MTLTexture> temp2 = [loader newTextureWithData:tempData options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil];
    id<MTLTexture> temp3 = [loader newTextureWithCGImage:cgRef options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil];
}] resume];