Compare 2 images, and export the difference to txt file

[philhung]

Hi All,

I use the command to find the difference between the below 2 images

https://photos.app.goo.gl/HzrdYycdhgbBacZ19
https://photos.app.goo.gl/9ckbkprJwezqDCJM7

Code: Select all

Compare -compose src c:\black1.png c:\black2.png c:\black_diff.png

the below is the output image
https://photos.app.goo.gl/UwNqWWgN3cXWQNjL7

and I want to convert that output image with difference only to be txt file for data processing by the below 2 commands.

output file size very large...

Code: Select all

convert c:\black_diff.png -transparent "#CCCCCC" sparse-color: c:\a.txt

output file contains nothing...

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convert c:\black_diff.png -transparent "#CCCCCC" sparse-color: > c:\b.txt

thanks for your help in advance!!!

[snibgo]

black_diff.png already has transparency, and the search for opaque pixels #CCCCCC finds none. You can "-alpha off" to remove any transparency.

[philhung]

Many thanks for your reply.
I still have few questions

1. how we know that black_dif.png with transparency?? is it I use Compare to find the difference??
2. I tried the below command with -alpha off, just want to make sure my understanding is correct

Code: Select all

convert c:\black_diff.png -transparent "#CCCCCC" -alpha off sparse-color: > c:\b.txt

thanks!!

[snibgo]

You should turn alpha off before the search:

Code: Select all

convert c:\black_diff.png -alpha off -transparent "#CCCCCC" sparse-color: > c:\b.txt

[philhung]

many thanks for your support!!!