Compare multipage tiff

[anthony]

Currently Im comparsions only work with two images at a time. If fact attempting multi-image iages would probably result in the first time images of the first file being compared, not the first image from each file.

I do have some plans for a future -layers function that merges pairs of 'shuffled' images using alpha composition as a means of merging GIF animations. This could be used get convert two multi-image files into a single multi-image 'difference' file. however I have been busy with other things, and have not gotten back to creating the shuffle, or the mutli-composition layers function. no ETA either, sorry.

[ZAB]

Did multipage images comparison ever worked in imagemagick?

[anthony]

actually yes...

Though not as I envisioned then above.

The operation is
-layers composition

See IM examples, Animation Modifications, Multi-Image Composition
http://www.imagemagick.org/Usage/anim_mods/#composite

For comparing images you would use 'difference' on the two sets of images.

For an example of that look at. the first example in
IM examples, Animation Modifications, Splitting up an Animation
http://www.imagemagick.org/Usage/anim_mods/#split

This compares a sequence of images with itself (shifted by one), and merged results.
That is create a mask of any difference between any image in the list.

[ZAB]

I do not want to split animation into frames. I just want to compare two multipage tiffs. I tried to run "compare -metric PSNR multipage1.tif multipage2.tif diff.tif" and it fails. Even though both tiffs are equal IM shows 11.7 PSNR and diff.tif contains only one meaningless page.

[anthony]

The pointer was not to what was being done, but to the compare (difference composite) aspect of that example.

[ZAB]

Ok. Is there any way to compare multipage tiffs on a page by page basis? With a one line command.

[anthony]

compare image_set_1.tiff null: image_set_2.tiff -compose differance -layers composite difference_image_set.tiff

Now the next step in how you want to 'examine the differences' is where metrics come in.

[ZAB]

I am getting this error "compare.exe: unrecognized option `-layers' @ error/compare.c/CompareImageCommand/707."

But even if I remove -layers from command line, say "compare -metric psnr multipage.tif null: multipage.tif diff.tif", IM prints 11.0495 PSNR to standard output. I'ts not how it should work on identical multipage files. For identical files it should print 1.#INF. Or throw an error that multipage files are unsupported....

[fmw42]

compare image_set_1.tiff null: image_set_2.tiff -compose differance -layers composite difference_image_set.tiff

I think Anthony may have meant

convert image_set_1.tiff null: image_set_2.tiff -compose differance -layers composite difference_image_set.tiff

Then you must analyze the difference image to get some metric for the difference such as the average or mean or rmse over the image

[ZAB]

Ok... It will be a second command line but how to calc PSNR of this diff image using only IM?

Comparing multipage images is a real usecase! Now IM silently compare first two pages of a first tiff file... or last two pages of a second file... whatever... it is a bug. Should I fill an issue in the issue tracker?

[anthony]

I think Anthony may have meant
convert image_set_1.tiff null: image_set_2.tiff -compose differance -layers composite difference_image_set.tiff

Yes.. Applogies. Brain thinking one thing, fingers typing another.

[vinayzz]

Any Update on the solution here?

[fmw42]

Any Update on the solution here?

This is an old post and a solution was given.

Please elaborate on your specific issue with examples and code. Or open a new topic.