Editing RGBA color model (section)

=== ARGB32 ===

The channels are arranged in memory in such manner that a single 32-bit unsigned integer has the alpha sample in the highest 8 bits, followed by the red sample, green sample and finally the blue sample in the lowest 8 bits:

[[File:PixelSamples32bppRGBA.png|none|Sample layout in a typical 32bpp pixel]]

ARGB values are typically expressed using 8 [[hexadecimal]] digits, with each pair of the hexadecimal digits representing the values of the Alpha, Red, Green and Blue channel, respectively. For example, <code>80FFFF00</code> represents 50.2% opaque (non-premultiplied) yellow. The <code>80</code> hex value, which is 128 in decimal, represents a 50.2% alpha value because 128 is approximately 50.2% of the maximum value of 255 (FF hex); to continue to decipher the <code>80FFFF00</code> value, the first <code>FF</code> represents the maximum value red can have; the second <code>FF</code> is like the previous but for green; the final <code>00</code> represents the minimum value blue can have (effectively – no blue). Consequently, red + green yields yellow. In cases where the alpha is not used this can be shortened to 6 digits <code>RRGGBB</code>, this is why it was chosen to put the alpha in the top bits. Depending on the context a <code>0x</code> or a number sign (#)<ref>[http://msdn.microsoft.com/en-us/library/system.windows.media.color(v=vs.95).aspx Microsoft MSDN XAML Color Structure reference] (XAML/WPF/Silverlight), including <code>#aarrggbb</code> and <code>sc# scA,scR,scG,scB</code></ref> is put before the hex digits.

This layout became popular when 24-bit color (and 32-bit RGBA) was introduced on personal computers. At the time it was much faster and easier for programs to manipulate one 32-bit unit than four 8-bit units.

On little-endian systems, this is equivalent to BGRA byte order.  On big-endian systems, this is equivalent to ARGB byte order.