readImageData method
Implementation
void readImageData(InputBuffer input, PsdImage psd) {
for (var i = 0; i < channels.length; ++i) {
channels[i].readPlane(input, width, height, psd.depth);
}
layerImage = PsdImage.createImageFromChannels(
psd.colorMode, psd.depth, width, height, channels);
}