Blending

Inochi2D allows for porter-duff blending modes to be applied to Part nodes and Composite nodes, these blending nodes affect how colors are mixed on compositing with the screen.

Additionally the special blending modes “Clip to Lower” and “Slice from Lower” are supported to provide a nicer looking but less flexible form of masking.

Rendering equations

Mode	Equation	Src	Dst	Src (Alpha)	Dst (Alpha)
Normal	Add	1	1-SrcAlpha
Multiply	Add	DstColor	1-SrcAlpha
Screen	Add	1	1-SrcColor
Lighten	Max	DstColor	1
Color Dodge	Add	DstColor	1
Linear Dodge	Add	1	1-SrcColor	1	1-SrcAlpha
Add (Glow)	Add	1	1	1	1-SrcAlpha
Subtract	ReverseSubtract	1-DstColor	1
Exclusion	Add	1-DstColor	1-SrcColor	1	1
Inverse	Add	1-DstColor	1-SrcAlpha
Destination In	Add	0	SrcAlpha
Clip to Lower	Add	DstAlpha	1-SrcAlpha
Slice from Lower	Add	0	1-SrcAlpha

Blend Accuracy Extension

Inochi2D provides the I2D_BLEND_ACCURACY extension, this extension is entirely implementation side.

If the Inochi2D implementation indicates support for this extension, it means that instead of emulating porter and duff blending modes, it will use GPU extensions to implement them properly.

This extension affects the rendering of the following blending modes.

• Normal

• Multiply

• Screen

• Lighten

• Color Dodge

• Subtract

• Inverse

This extension additionally affects the rendering of the following blending modes if I2D_EXTENDED_BLEND_MODES is supported.

• Overlay

• Darken

• Color Burn

• Hard Light

• Soft Light

• Difference

• Exclusion

Implementation Notes

• This extension can be implemented in OpenGL via the GL_KHR_blend_equation_advanced and GL_KHR_blend_equation_advanced_coherent extensions.

• This extension can be implemented in Vulkan via the VK_EXT_blend_operation_advanced extension.

• This extension can be implemented on tiler GPUs, such as PowerVR and Apple Silicon chips, via framebuffer fetch.

This extension was introduced in Inochi2D 0.8 Standard.

Extended Blend Modes

Inochi2D provides the I2D_EXTENDED_BLEND_MODES extension.

This extension adds support for the following blending modes.

• Overlay

• Darken

• Color Burn

• Hard Light

• Soft Light

• Difference

• Exclusion

Implementation Notes

• This extension can be emulated by shaders using Texture Barriers.

• This extension can be emulated by shaders using a ping-pong framebuffer setup, this is unoptimal.

This extension was introduced in Inochi2D 0.8 Standard.

This extension is influenced by I2D_BLEND_ACCURACY.