Assembly: Microsoft.Xna.Framework.Graphics (in microsoft.xna.framework.graphics.dll)
In the XNA Framework, all two-dimensional (2D) images are represented by a range of memory called a surface. Within a surface, each element holds a color value representing a small section of the image, called a pixel. An image's detail level is defined by the number of pixels needed to represent the image and the number of bits needed for the image's color spectrum. For example, an image that is 800 pixels wide by 600 pixels high with 32 bits of color for each pixel (written as 800 x 600 x 32) is more detailed than an image that is 640 pixels wide by 480 pixels tall with 16 bits of color for each pixel (written as 640 x 480 x 16). Likewise, the more detailed image requires a larger surface to store the data. For an 800 x 600 x 32 image, the surface's array dimensions are 800 x 600, and each element holds a 32-bit value to represent its color.
All formats are listed from left to right, most-significant bit to least-significant bit. For example, ARGB formats are ordered from the most-significant bit channel A (alpha), to the least-significant bit channel B (blue). When traversing surface data, the data is stored in memory from least-significant bit to most-significant bit, which means that the channel order in memory is from least-significant bit (blue) to most-significant bit (alpha).
The default value for formats that contain undefined channels (Rg32, Alpha8, and so on) is 1. The only exception is the Alpha8 format, which is initialized to 000 for the three color channels.