Allow Comparison of Optimized images with Unoptimized #140
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
@reidmain As an outside contributor I the repo will not allow me to add requested reviewers. I'm curious to know if there's anything else needed from me in order to get this PR considered? Please let me know. |
Happy to review, maybe you can rebase against latest so we can run the CI on this to see if it breaks the integration tests we have. |
Optimized images may contain the same image, but fewer color components and therefore fewer bits per row. This causes the current image comparison to fail even though the image is otherwise identical.
tinder-owenthomas
force-pushed
the
oht/allow-comparison-of-optimized-pngs-with-unoptimized-pngs
branch
from
934dc4f
to
8e9c24f
Compare
|
Sorry @alanzeino, just saw your comment now. I've updated from latest |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Optimized images (such as those generated by
pngcrush) contain the same image in many fewer bytes of data. One of the optimizations can convert an image from the normal 4 color channels to only 2 if there are few enough colors in an image (such as images that only use black, white, and gray). This causes fewer color components therefore fewer bits per row. This in turn causes the current image comparison calculation to fail even though the images contain identical pixels because the amount of memory they consume is different.This update makes sure the CGBitmapContext is created with the same amount of memory for both images being compared, even though it is technically unnecessary for the optimized image. In this way, the raw memory of the resulting image pixels drawn into the contexts is still identical and easily comparable.
This change will allow us to crush all the snapshot images in our repo, saving us hundreds of MB of files on every clone into CI and CD.
This PR also adds 2 new tests to verify that optimized images can be compared with unoptimized, and the other way around. This requires the addition of one new image (rect_crushed.png) which is a crushed version of rect.png using default
pngcrushoptions which reduces the file size by ~67% while retaining identical pixel information.