Raster Image

Updated 22 Sep 2026

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What it is
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  an image represented as a grid of pixel values
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Representaion
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  grayscale - typically an $H\times W$ array
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  RGB - typically an $H\times W\times3$ array
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  RGB with alpha - typically an $H\times W \times 4$ array
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Storage example
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  an uncompressed $640 \times 480$ image with three 8-bit channels contains $640 \cdot 480 \cdot 3 = 921{,}600$ bytes of pixel data before headers, padding, or metadata
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Caution
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  compressed file size can differ greatly from the decoded array size
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  "bitmap" can refer generically to a raster representaiton; BMP is one specific file format
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Distinguish from
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  Vector Graphics

Linked references 2