It is sometimes advantageous to use square images, such as 64x64, 128x128, or 256x256. Others have noted that this constraint is not as relevant as things progress. Some have reported having excellent success with non-square images, across various platforms. Some examples of when square textures are advantageous are given below. In many cases, the power of 2 rule leads naturally to a square image.
Square images lead to an efficient packing structure for montages.
For example, four 128x128 images can be combined into one 256x256 texture, reducing overall file size a bit and reducing http fetch requirements by a factor of 4. Of course, non-square textures can also be montaged, such as two 256x128 textures stacked to make a 256x256 image. A Square Image was designed with square, power of 2 images in mind. It is also strongly influenced by our work in the consumer digital photography marketplace. The increments on the target size slider are 16, with a page size of 64.