3000 x 3000 x 3 bytes/pix = 25.7 Megabytes!!, if you are using 24 bpp images, and more if you use 32 bpp. You can use 16 bpp to reduce this. The Wiz memory free for apps is about 20 Mb or less if I remember. You can consider access the file by blocks, that is, reading only certain square areas...