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PNG loader: attach palette bit depth, if any, as metadata #1199

Merged

jcupitt merged 1 commit into libvips:master from lovell:png-header-palette-bit-depth

Jan 1, 2019

Member

lovell commented Jan 1, 2019 •

edited

Hello, this is a small addition to the PNG header reader to attach the bit depth of the palette, if any, as metadata.

By way of example, using test images from http://www.schaik.com/pngsuite/pngsuite_bas_png.html we can now differentiate 4-bit vs 8-bit palette:

$ vipsheader -a basn3p04.png
basn3p04.png: 32x32 uchar, 3 bands, srgb, pngload
width: 32
height: 32
bands: 3
format: uchar
coding: none
interpretation: srgb
xoffset: 0
yoffset: 0
xres: 2.834
yres: 2.834
filename: basn3p04.png
vips-loader: pngload
palette-bit-depth: 4

$ vipsheader -a basn3p08.png
basn3p08.png: 32x32 uchar, 3 bands, srgb, pngload
width: 32
height: 32
bands: 3
format: uchar
coding: none
interpretation: srgb
xoffset: 0
yoffset: 0
xres: 2.834
yres: 2.834
filename: basn3p08.png
vips-loader: pngload
palette-bit-depth: 8

These two images would otherwise be indistinguishable using metadata alone.


          PNG loader: attach palette bit depth, if any, as metadata

7854ead

jcupitt merged commit 2b8db2e into libvips:master

Member

jcupitt commented Jan 1, 2019

OK, looks reasonable.

lovell deleted the png-header-palette-bit-depth branch

January 1, 2019 20:35

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