glsl-blend

Photoshop blending modes in glsl for use with glslify. Blending modes include Screen, Multiply, Soft Light, Vivid Light, Overlay, etc. Implementations sourced from this article on Photoshop math.

Demo

http://jamieowen.github.io/glsl-blend

Installation

npm install glsl-blend

Standard Usage

Blend modes can be imported individually using the standard glslify preprocessor syntax.

#pragma glslify: blendAdd = require(glsl-blend/add)
#pragma glslify: blendAverage = require(glsl-blend/average)
#pragma glslify: blendColorBurn = require(glsl-blend/color-burn)
#pragma glslify: blendColorDodge = require(glsl-blend/color-dodge)
#pragma glslify: blendDarken = require(glsl-blend/darken)
#pragma glslify: blendDifference = require(glsl-blend/difference)
#pragma glslify: blendExclusion = require(glsl-blend/exclusion)
#pragma glslify: blendGlow = require(glsl-blend/glow)
#pragma glslify: blendHardLight = require(glsl-blend/hard-light)
#pragma glslify: blendHardMix = require(glsl-blend/hard-mix)
#pragma glslify: blendLighten = require(glsl-blend/lighten)
#pragma glslify: blendLinearBurn = require(glsl-blend/linear-burn)
#pragma glslify: blendLinearDodge = require(glsl-blend/linear-dodge)
#pragma glslify: blendLinearLight = require(glsl-blend/linear-light)
#pragma glslify: blendMultiply = require(glsl-blend/multiply)
#pragma glslify: blendNegation = require(glsl-blend/negation)
#pragma glslify: blendNormal = require(glsl-blend/normal)
#pragma glslify: blendOverlay = require(glsl-blend/overlay)
#pragma glslify: blendPhoenix = require(glsl-blend/phoenix)
#pragma glslify: blendPinLight = require(glsl-blend/pin-light)
#pragma glslify: blendReflect = require(glsl-blend/reflect)
#pragma glslify: blendScreen = require(glsl-blend/screen)
#pragma glslify: blendSoftLight = require(glsl-blend/soft-light)
#pragma glslify: blendSubtract = require(glsl-blend/subtract)
#pragma glslify: blendVividLight = require(glsl-blend/vivid-light)

A foreground and background color is needed to perform a blend operation.

#pragma glslify: blend = require(glsl-blend/screen)

void main() {
    vec4 bgColor = texture2D(bg, vUv);
    vec4 fgColor = texture2D(foreground, vUv);

    vec3 color = blend(bgColor.rgb, fgColor.rgb);
    gl_FragColor = vec4(color, 1.0);
}

Blend modes can also specify an additional opacity parameter.

float opacity = 0.75;
vec3 color = blend(bgColor.rgb, fgColor.rgb, opacity );

Modal Usage

The demo shows all blend modes switchable via a drop down.

For this, there is an additional 'all' glsl function that can be required to import all blend mode functions at once and specify which one to use via an integer. Integers for each blend mode can be imported using the javascript modes module, and passed as a uniform to the shader.

// javascript
var modes = require( 'glsl-blend/modes' );

// using stackgl
myShader.uniforms.blendMode = modes.HARD_LIGHT;

// glsl
#pragma glslify: blend = require(glsl-blend/all)
uniform int blendMode;

// ...

vec3 color = blend( blendMode, bgColor.rgb, fgColor.rgb, 0.75 );

Todo

• Add Hue, Luminance, Saturation & Color Modes.
• Implement color conversion functions for the above as separate glsl modules.

Contributing

See stackgl/contributing.

License

MIT. See LICENSE.md for details.