How much effect does image tile size (not mosaic sheet tile size) have on cache requirements?
This can be dramatic. Image data are accessed as stored units of image tile size or image scan line size. Because the image tile/stripe is the ‘quatum’ unit of image data I/O, it means that this much data must be loaded into memory even if only a single pixel is required for a compuation. Therefore the cache data use efficiency would be highest if stripes/tiles contained only a single pixel! However, if that were the case, then the disk I/O overhead would become overwhelming. Thus, optimal tile/strip size is a balance between “big enough for good disk I/O performance” and “small enough to avoid loading unnecessary data into the cache. For example: assume a color TIFF image, 12000 pixels wide with file format using stripe storage with 5 scan lines per strip. This means that image data are accessed (read and write) in units of 180000 bytes (5(lines)*12000(pixel)*3(rgb)) bytes at a time. (Note that color data are stored in memory as 4 bytes to greatly enhance speed – at the expense of inc
