A filter that performs a histogram specification operation on an image.
- iOS 9.0+
- macOS 10.13+
- Mac Catalyst 13.0+
- tvOS 9.0+
- Metal Performance Shaders
MPSImage is a generalized version of histogram equalization operation. The histogram specification filter converts the image so that its histogram matches the desired histogram.
The process is divided into three steps:
init(device:method to create a
encodemethod. This creates a privately held image transform which will convert the distribution of the source histogram to the desired histogram. This process runs on a command buffer when it is committed to a command queue. It must complete before the next step can be run. It may be performed on the same command buffer. The
Transform(to: source Texture: source Histogram: source Histogram Offset: desired Histogram: desired Histogram Offset:)
sourceargument is used by the method to determine the number of channels and therefore which histogram data in the source histogram buffer to use. The source histogram and desired histogram must have been computed either on the CPU or using the
encode(commandmethod to read data from the source texture, apply the equalization transform to it, and write to the destination texture. This step is also done on the GPU on a command queue.
Buffer: source Texture: destination Texture:)