Simple hash of PIL image

Question

Background

I want to store information of PIL images in a key-value store. For that, I hash the image and use the hash as a key.

What I tried

I h

Answer 1

Recognising what you say about timestamps, ImageMagick has exactly such a feature. First, an example.

Here I create two images with identical pixels but a timestamp at least 1 second different:

convert -size 600x100 gradient:magenta-cyan 1.png
sleep 2
convert -size 600x100 gradient:magenta-cyan 2.png

If I checksum them on macOS, it tells me they are different because of the embedded timestamp:

md5 -r [12].png

c7454aa225e3e368abeb5290b1d7a080 1.png
66cb4de0b315505de528fb338779d983 2.png

But if I checksum just the pixels with ImageMagick, (where %# is the pixel-wise checksum), it knows the pixels are identical and I get:

identify -format '%# - %f\n' 1.png 2.png
70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 1.png
70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 2.png

And, in fact, if I make a TIFF file with the same image contents, whether with Motorola or Intel byte order, or a NetPBM PPM file:

convert -size 600x100 gradient:magenta-cyan -define tiff:endian=msb 3motorola.tif
convert -size 600x100 gradient:magenta-cyan -define tiff:endian=lsb 3intel.tif
convert -size 600x100 gradient:magenta-cyan 3.ppm

ImageMagick knows they are the same, despite different file format, CPU architecture and timestamp,:

identify -format '%# - %f\n' 1.png 3.ppm 3{motorola,intel}.tif

70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 1.png
70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 3.ppm
70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 3motorola.tif
70680e2827ad671f3732c0e1c2e1d33acb957bc0d9e3a43094783b4049225ea5 - 3intel.tif

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So, in answer to your question, I am suggesting you shell out to ImageMagick with the Python subprocess module and use ImageMagick.