https://bugs.kde.org/show_bug.cgi?id=449409
Bug ID: 449409
Summary: Stair Step Image Scaling
Product: krita
Version: 5.0.0
Platform: Mint (Ubuntu based)
OS: Linux
Status: REPORTED
Severity: wishlist
Priority: NOR
Component: Resize/Scale Image/Layer
Assignee: krita-bugs-n...@kde.org
Reporter: supineb...@protonmail.com
Target Milestone: ---
This is a feature request, for the addition of a stair step scaling method in
Scale to New Size module. In GUI, I envisage an extra line under 'filter' and
above 'print size', with a heading of something like 'scaling %', and options
of 'normal' or 'stair stepping 10%'. Better names can no doubt be thought of.
The method of applying stair step scaling is as follows:
1. Current Image Width – Desired Image Width = Width Difference [eg. 3258 -
2056 = 1202]
2. Width Difference * 0.1 = Increment Size [eg. 1202 * 0.1 = 120.2]
3. Current Image Width – Increment Size = New Image Width [eg. 3258 - 120.2
= 3137.8]
4. Repeat 3 until Desired Image Width is reached. [eg. 3137.8 - 120.2 =
3017.6, etc…]
It can work with any scaling algorithm.
Note: Stair Stepping method is only superior to normal method when the image is
scaled in linear colour space. Therefore, it might be a good idea to make the
option unavailable in non-linear spaces. An alternate option would be to
convert from non-linear to linear to perform the operation, then back to
linear, however this may be problematic if the image is 8 bit, as going from 8
bit non-linear to 8 bit linear can create banding in the shadows. So to
summarise, this method is only useful if the user is either 1) Working in
linear colour space, or 2) Working in 16 bit or more non-linear colour space,
allowing the conversion to linear and back to perform the operation.
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