Provide option to use bilinear filtering for resizing masks/grayscale images #16347
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…ault) * Lanczos is a good default when resizing, however, it is suboptimal for masks as it can introduce ringing artifacts. So use bilinear in these situations. * Bicubic is better than Lanczos here, but can introduce "pinching" on corners. Nearest would be optimal for binary masks, but much worse if there's any blurring. * Adds a new toggle to the img2img settings, which is disabled by default, as it does affect the shape of masks compared to Lanczos.
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Description
The fallback resizing option in
resize_imageis Lanczos, which is a good default in the majority of cases. However, when resizing grayscale images, in particular masks, it can introduce ringing artifacts. A better option in this case is bilinear filtering. You can see the difference in the filters in the provided image (which are outputs of the cropping masks used in img2img during ADetailer processing with mask blurring set to zero).Both nearest and bicubic were considered, however:
To this end, this commit introduces a new option in the img2img settings (disabled by default) that allows the use of bilinear filtering when resizing, if the incoming image is grayscale (PIL's mode 'L'). In all other cases, Lanczos is used as is the case currently.
I've made it a toggle because it does alter the shape of the mask enough to potentially affect current workflows. The effect is also very subtle (as evidenced by the image), but I would argue is more correct.
Screenshots/videos:
Checklist: