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system, where the two mnemonics are reverses of each other. Therefore, to be unambiguous, it is important to state which ordering is used when referring to the encoding. This article will use a scheme that has some popularity, which is to add the suffix "8888" to indicate if 4 8-bit units or "32" if
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of these four bytes in memory can differ, which can lead to confusion when image data is exchanged. These encodings are often denoted by the four letters in some order (most commonly RGBA). The interpretation of these 4-letter mnemonics is not well established. There are two typical ways to
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In the byte-order scheme, "RGBA" is understood to mean a byte R, followed by a byte G, followed by a byte B, and followed by a byte A. This scheme is commonly used for describing file formats or network protocols, which are both
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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:
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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.
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by the alpha value, and if they are it does not state what color space that premultiplication was done in. This means more information than just "RGBA" is needed to determine how to handle an image.
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In many systems when there are more than 8 bits per channel (such as 16 bits or floating-point), the channels are stored in RGBA order, even if 8-bit channels are stored in some other order.
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In the word-order scheme, "RGBA" is understood to represent a complete 32-bit word, where R is more significant than G, which is more significant than B, which is more significant than A.
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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
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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
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would be Red and Green:50.2%, Blue:0% and Alpha:100%, a brown. This is what you would get if RGBA8888 data was read as words on these machines. It is used in
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digits, with each pair of the hexadecimal digits representing the values of the Alpha, Red, Green and Blue channel, respectively. For example,
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On little-endian systems, this is equivalent to BGRA byte order. On big-endian systems, this is equivalent to ARGB byte order.
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Example of an RGBA image composited over a checkerboard background. alpha is 0% at the top and 100% at the bottom.
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In some contexts the abbreviation "RGBA" means a specific memory layout (called
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The bytes are stored in memory on a little-endian machine in the order ABGR.
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represents 50.2% opaque (non-premultiplied) yellow. The
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represents the maximum value red can have; the second
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73:Learn how and when to remove these messages
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654:#aarrggbb
532:talk page
415:RGBA8888
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303:4D vector
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