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Based on the PNGsuite. The following samples test the delta-image PROM function. The top image shows what the following MNG sample should look like. If there are any discrepencies, your MNG decoder does not handle the PROM chunk adequately. This will always be the case for implementations based on libmng-1.0.4 or older.
In this sample the original images are non-interlaced and the 'left-bit-replication' option of the PROM chunk is used for the promotion operation.
The first row of the sample shows the original images. For each subsequent row each original image is 'promoted' to a higher level (where possible). So the second row shows the 1-bit grayscale input promoted to 2-bit grayscale, the next row shows 1- & 2-bit grayscale images promoted to 4-bit grayscale, etc. Impossible promotions are marked with a red cross.

PROM-BASN-repl.mng
Some or all of the following images were used: basn6a16 & basi6a16 - 3x16 bits rgb color + 16 bit alpha-channel basn6a08 & basi6a08 - 3x8 bits rgb color + 8 bit alpha-channel basn4a16 & basi4a16 - 16 bit grayscale + 16 bit alpha-channel basn4a08 & basi4a08 - 8 bit grayscale + 8 bit alpha-channel
basn3p08 & basi3p08 - 8 bit (256 color) paletted
basn3p04 & basi3p04 - 4 bit (16 color) paletted
basn3p02 & basi3p02 - 2 bit (4 color) paletted
basn3p01 & basi3p01 - 1 bit (2 color) paletted
basn2c16 & basi2c16 - 3x16 bits rgb color
basn2c08 & basi2c08 - 3x8 bits rgb color
basn0g16 & basi0g16 - 16 bit (64k level) grayscale
basn0g08 & basi0g08 - 8 bit (256 level) grayscale
basn0g04 & basi0g04 - 4 bit (16 level) grayscale
basn0g02 & basi0g02 - 2 bit (4 level) grayscale
basn0g01 & basi0g01 - black & white

Samples on this page are Copyright © G. Juyn Images used in the samples are Copyright © Willem van Schaik

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