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Thread: Color depth description

  1. #1
    IV Newbie
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    Jun 2020
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    Default Color depth description

    Hello Forum,
    I am wondering whether I understand the dialog box for color depth reduction correctly. It states:

    65536 colors (24 BPP, simple RGB-565)
    256 colors (8 BPP)
    etc.

    I assume, that BPP stands for bits-per-pixel; and RGB-565 means 5 bits for red, 6 bits for green, and 5 bits for blue, right.
    24 BPP encode 16,777,216 colors, and 16 BPP encode 65536 colors.

    I think there is a typo and the number of colors should match BPP?

    Best regards

  2. #2
    Moderator Enterprise User Bhikkhu Pesala's Avatar
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    Default

    2^24 = 16,777,216
    2^8 = 256

  3. #3
    Power User j7n's Avatar
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    Jun 2006
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    IrfanView 4.51
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    Default

    16-bit color depth is rescaled to 0-255 range afterwards and occupies 24 bits. It is not possible to produce true 565 output with IrfanView or most modern software. This option is rather pointless. All it does is achieve slight posterization, which might help increase compression ratio.

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