I'm trying to replicate blending two images in Photoshop with CIFilters in Swift. Let's say I want to blend img1 and img2 with softLight, then in Swift I can do:
let blendSoftLight = CIFilter.softLightBlendMode()
blendSoftLight.backgroundImage = img1
blendSoftLight.inputImage = img2
This works and I'll get the same result as in Photoshop. But in Photoshop you can blend with opacity, so if I want to blend img2 and img1 with soft light and 50% opacity - is this possible with CIFilter in Swift?
I have tried different methods, like blending img1 and img2 as above, and then blend the resulting image with the original image with CIFilter.blendWithAlphaMask(), with a 50% alpha mask. But the result is of course not the same as the blendWithAlphaMask only does a "normal" blend, it's not using soft light blend mode.
From the docs of the CISoftLightBlendMode filter it appears the only parameters it takes are inputImage and inputBackgroundImage. It doesn't appear that it lets you vary the opacity of the 2 images that it blends together. You might be able to apply an alpha channel to one or the other image before blending in order to change its opacity.