int y1 = Math.min(y0 + cm.getScanLinesPerBlock() - 1, dw.getYMax());
Box2i block = new Box2i(x0, y0, x1, y1);
int blockSize = computeTileSize(block);
for (int y = y0; y <= y1; y++) {
for (Channel channel : chlist.channels()) {
String name = channel.getName();
int sx = channel.getxSampling();
int sy = channel.getySampling();
if (y % sy == 0) {
int nx = 1 + (x1 - x0 - (x1 % sx)) / sx;