swap blend and base params to match effects in Photoshop

[kfitfk]

When testing out the blend modes, I noticed that "Color Burn", "Color Dodge", "Soft Light", and "Hard Light" effects using pixi/picture are different from effects in Photoshop.

I've made a simple demo. The image on the left is rendered using pixi/picture, the image on the right is exported from Photoshop.

Here's the demo code and psd file.
demo_code_and_psd.zip

For most of the blend modes, I swapped the blend and base parameters.

As with hard light, it is the same as overlay except that they expect layers in reverse order from each other. Since the 3rd parameter of mix function for overlay is step(base, 0.5), the corresponding param for hard light should be 1.0 - step(base, 0.5), not 1.0 - step(blend, 0.5).