[Image Resizer] Resized image is blurry #10675
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Pingumania
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Issue-Bug
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Notes:
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crutkas
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Priority-2
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doing the tweak i think is easy, doing the testing here is where most of the time will be spent. need to validate
validate we didn't break other formats |
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What kind of algorithm does Image Resizer use? Is it always the same or can we use different for enlargement versus smaller? |
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To add a data point with more details - anime screenshot:
Even with the same quality settings (confirmed with Irfanview on the exported images) Alternating the scaling interpolation in GIMP in all cases (None, Linear, Cubic interpolation) looks better. (Linear looks worse than Cubic, but still better than Image Resizer. None has no blur.) |
Jay-o-Way
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Status-Reproducible
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Project From what I can see, the blurring issue limitation is a given from that standard lib. I don't see any parameters beyond the scale factors/transformation matrix. reference docs |
Fixes microsoft#10675 In some cases a resized image becomes very blurry. Loading the input image file into cache in BitmapDecoder resolves the blurriness. --- I tried to find the technical reason why caching resolves it, or why it is blurry in the first place, but was unable to locate it. The issue seems to occur only on specific images. I was not able to identify a strong parameter that would cause it. Nevertheless, with the images I will attach to the PR, I hope to make an evident case for the factual resolution of the issue. And maybe or hopefully someone with more knowledge about the respective used APIs will be able to provide the factual, technical reason for it. --- `ResizeOperation` uses `BitmapDecoder` to load the image file. In main the decoder is instantiated with `BitmapCacheOption.None`. Changing it to `BitmapCacheOption.OnLoad` resolves the issue. The pass-along of image data is as follows: 1. create decoder 2. decoder -> image file metadata 3. decoder -> `BitmapFrame` -> `TransformedBitmap` -> `BitmapFrame` -> encoder (`Frames.Add()`) -> `encoder.Save()` --- [transformdoc] mentions the following about loaded cached image data potentially mismatching target pixel size, which made me wonder whether the no-cache delayed reading in combination with the transformation leads to reduced-size-reading. I was not able to confirm it. Given that most images I tested did not have a problem, I don't think it's a plausible cause. > If you don't do this, the application will cache the image as though it were rendered as its normal size rather than just the size that is displayed. [transformdoc]: https://learn.microsoft.com/en-us/dotnet/desktop/wpf/graphics-multimedia/how-to-apply-a-transform-to-a-bitmapimage --- For multiple test images, any differences were hard to spot, they did not result in blurriness. The image I had issues with in the past being very colorful made me wonder whether amount of color information could make the difference. But with the technical context, that would only make sense if the encoder caching somehow handled color information differently, which seems unlikely too.
microsoft-github-policy-service
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Status-In progress
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I would appreciate feedback in draft PR #32797 |
Microsoft PowerToys version
0.35.0
Running as admin
No
Area(s) with issue?
Image Resizer
Steps to reproduce
I took a random screenshot and resized it with Image Resizer and Paint to have a width of 600.
I used 95 jpeg quality and "fit 600x600 pixel".
The measurements of the orignal screenshot are 1213x750.
The measurements of the Paint image are 600x370.
The measurements of the Image Resizer one are 600x371.
Here are the images
Original
Image Resizer
Paint
✔️ Expected Behavior
The Image Resizer picutre shouldn't be blurry.
❌ Actual Behavior
The picture from the Image Resizer is blurry compared the one from Paint.
Other Software
No response
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