My recommendation would be to use imresize to reduce the number of rows/columns in your array before you plot it. Whether you use imresize or not, as other have mentioned, because your screen doesn't have 32,000 pixels horizontally or vertically, the picture you see on the screen will have to be downsampled somehow. If you use imresize you control the method used for the downsampling, and you have a large range of options. This will likely be faster than relying on the imagesc command to do the downsampling, and imagesc offers only two choices for how to do the downsample (rather than the 8 or so options offered by imresize).
