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Based on the PNGsuite.

The following samples test various delta-image variations on grayscale targets with an alpha channel.

In each sample the top row of images is displayed against a plain background to show the original image that is used in delta-operations below it. A background for the remaining canvas is generated from a grayscale+alpha image with respectively 8 or 16 bits bit_depth (subsequent samples). For each a sample with a complete white and a complete black background are shown.

Below the original images, the first 2 rows shows a pixel-replace (4) and pixel-addition (1) operation respectively. This is only possible for grayscale+alpha delta's (the last 2 original images). The next two rows show a color-replace (5) and color-addition (2) operation respectively. The bottom two rows show an alpha-replace (6) and alpha-addition (3) operation. These last 4 rows are only possible with single-channel delta's (the first 5 original images).

The results will look bizar in most cases!

The left side of each sample shows a screenshot of what the right side should look like. If they do not match, your MNG decoder doesn't handle delta-image variations very well. Note that this will be the case for implementations using libmng-1.0.4 or older!





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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