Improve performance of grayscale calculation steps#2
Open
developher-net wants to merge 2 commits intojosefrichter:masterfrom
Open
Improve performance of grayscale calculation steps#2developher-net wants to merge 2 commits intojosefrichter:masterfrom
developher-net wants to merge 2 commits intojosefrichter:masterfrom
Conversation
Since the pixel rewrite loop will run literally thousands of times on just a single image, it makes sense to optimize it as much as possible. Reducing to a single iterative loop instead of two nested loops. Also reduce the math run inside of each loop to calculate the pixel position in the array.
The standard "Luma" formula is closer to how humans perceive colors and grayscale. While an average is technically correct, it doesn't match what the human eye perceives. See http://www.tannerhelland.com/3643/grayscale-image-algorithm-vb6/ for more explanation.
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
The grayscale calculation involving nested loops that check properties of the image on every loop are inefficient. On top of that, the extra calculation to determine the pixel position based on the interation of the nested loops adds more overhead
This can be collapsed into a single iterative loop, without an inner calculation. Considering this loop runs literally thousands of times on even a small image, simplification makes for a significant performance improvement.