iOS Sprite Kit - SKSpriteNode - blend two sprites - sprite-kit

Question

Actually, I'm migrating a game from another platform, and I need to generate a sprite with two images.
The first image will be something like the form, a pattern or stamp, and the second is only a rectangle that sets color to the first. If the color was plane, it will be easy, I could use sprite.color and sprite.colorBlendFactor to play with it, but there are levels where the second image is a rectangle with two colors (red and green, for example).
Is there any way to implement these with Sprite Kit?
I mean, something like using Core image filter, and CIBlendWithAlphaMask, but only with Image and Mask image. (https://developer.apple.com/library/ios/documentation/graphicsimaging/Reference/CoreImageFilterReference/Reference/reference.html#//apple_ref/doc/uid/TP40004346) -> CIBlendWithAlphaMask.
Thanks.

Answer 1

Look into the SKCropNode class (documentation here) - it allows you to set a mask for an image underneath it.
In short, you would create two SKSpriteNodes - one with your stamp, the other with your coloured rectangle. Then:
SKCropNode *myCropNode = [SKCropNode node];
[myCropNode addChild:colouredRectangle]; // the colour to be rendered by the form/pattern
myCropNode.maskNode = stampNode; // the pattern sprite node
[self addChild:myCropNode];
Note that the results will probably be more similar to CIBlendWithMask rather than CIBlendWithAlphaMask, since the crop node will mask out any pixels below 5% transparency and render all pixels above this level, so the edges will be jagged rather than smoothly faded. Just don't use any semi-transparent areas in your mask and you'll be fine.