PhotoDemon includes a classic Pinch and Whirl distortion tool. Both pinch and whirl amount allow for sub-pixel accuracy, and a radius can be specified to affect only a portion of the image.
Like other distortion tools in the program, five options are provided for dealing with off-canvas pixels (clamp, erase, ignore, reflect, wrap). A dedicated Quality option uses bilinear interpolation to further improve the quality of the final image.
Finally, like all PhotoDemon tools, a dedicated command bar allows you to save and load custom presets, randomize parameters, and reset to default values. Last-used settings are automatically saved and restored, and all changes provide a real-time preview (no click or mouse button release required).