Nothing else in Construct uses this, so there is not currently any mechanism for it. Further it's complicated because to balance memory usage and rendering performance, the sprite image data is either in storage in compressed format (therefore requiring loading and decompressing to access the image data), or uploaded to the GPU as a WebGL texture (where it can only be rendered, or if you are willing to kill GPU performance, read back to the CPU, in which case it will have also gone through a lossy alpha premultiplication). So I have to ask what do you need to use this for, and is it really the best/only way to do that?