CIImageAccumulator是做什么的？

Question

Problem

The apple documentation states when the CIImageAccumulater can be used, but unfortunately it does not say what it actually does.

The CIImageAccumulator class enables feedback-based image processing for such things as iterative painting operations or fluid dynamics simulations. You use CIImageAccumulator objects in conjunction with other Core Image classes, such as CIFilter, CIImage, CIVector, and CIContext, to take advantage of the built-in Core Image filters when processing images.

I have to fix code that used a CIImageAccumulator . It seems to me that all it is meant to do, despite its name, is to return a CIImage with all CIFilter s applied to the image. Adding the first image however darkens the output. That is not what I would expect from an accumulator nor from any other Operator that enables feedback based image processing.

Question

Can anyone answer what logic / algorithm is being used when setting and getting images in and out of the CIImageAccumulator

Answer 1

The biggest advantage of the CIImageAccumulater is that stores its contents between different rendering steps (in contrast to CIFilter or CIImage ). This allows you to use the state of a previous rendering step, blend it with something new and store that result again in the accumulator.

Apple's main use case is interactive painting: You retrieve the current image from the accumulator, blend a new stroke the user just painted with a gesture on top of it, and store the resulting image back into the accumulator. Then you display the content of the accumulator. You can read about it here .