AsepriteBlendFuncs

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ceramic.AsepriteBlendFuncs (Class)

Blending functions that operate at pixel/color level, ported from Aseprite source code.

This class provides a comprehensive set of blend modes compatible with Aseprite files, implementing standard compositing operations like multiply, screen, overlay, and more advanced modes like color dodge, soft light, and HSL-based blending.

All blending operations work with RGBA colors and support opacity/transparency. The implementations are optimized for performance with inline functions and platform-specific optimizations.

References:

  • W3C Compositing and Blending Level 1: http://dev.w3.org/fxtf/compositing-1/
  • Aseprite source: https://github.com/aseprite/aseprite
See: AsepriteData for usage in Aseprite file rendering

Static Members

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min(a: Int, b: Int): Int

Returns the minimum of two integers.

Name Type Description
a Int First value
b Int Second value
Returns Description
Int The smaller value
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max(a: Int, b: Int): Int
Name Type
a Int
b Int
Returns
Int
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abs(v: Int): Int
Name Type
v Int
Returns
Int
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half(v: Int): Int
Name Type
v Int
Returns
Int
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div(a: Int, b: Int): Int
Name Type
a Int
b Int
Returns
Int
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blendMultiply(b: Int, s: Int, t: Int): Int

Multiply blend mode: Darkens by multiplying colors. Result = backdrop * source

Name Type Description
b Int Backdrop (base) color component (0-255)
s Int Source color component (0-255)
t Int Temporary variable for optimization
Returns Description
Int Blended color component (0-255)
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blendScreen(b: Int, s: Int, t: Int): Int

Screen blend mode: Lightens by inverting, multiplying, and inverting again. Result = 1 - (1-backdrop) * (1-source)

Name Type Description
b Int Backdrop color component (0-255)
s Int Source color component (0-255)
t Int Temporary variable for optimization
Returns Description
Int Blended color component (0-255)
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blendOverlay(b: Int, s: Int, t: Int): Int
Name Type
b Int
s Int
t Int
Returns
Int
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blendDarken(b: Int, s: Int): Int
Name Type
b Int
s Int
Returns
Int
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blendLighten(b: Int, s: Int): Int
Name Type
b Int
s Int
Returns
Int
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blendHardLight(b: Int, s: Int, t: Int): Int
Name Type
b Int
s Int
t Int
Returns
Int
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blendDifference(b: Int, s: Int): Int
Name Type
b Int
s Int
Returns
Int
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blendExclusion(b: Int, s: Int, t: Int): Int
Name Type
b Int
s Int
t Int
Returns
Int
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blendColorDodge(b: Int, s: Int): Int

Color dodge blend mode: Brightens the backdrop to reflect the source. Result = backdrop / (1 - source)

Name Type Description
b Int Backdrop color component (0-255)
s Int Source color component (0-255)
Returns Description
Int Blended color component (0-255)
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blendColorBurn(b: Int, s: Int): Int
Name Type
b Int
s Int
Returns
Int
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blendSoftLight(_b: Int, _s: Int): Int

Soft light blend mode: Similar to overlay but softer. Uses a complex formula that creates a subtle lighting effect.

Name Type Description
_b Int Backdrop color component (0-255)
_s Int Source color component (0-255)
Returns Description
Int Blended color component (0-255)
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blendDivide(b: Int, s: Int): Int
Name Type
b Int
s Int
Returns
Int
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rgba(r: Int, g: Int, b: Int, a: Int): AlphaColor

Creates an AlphaColor from RGBA components.

Name Type Description
r Int Red component (0-255)
g Int Green component (0-255)
b Int Blue component (0-255)
a Int Alpha component (0-255)
Returns Description
AlphaColor ARGB color value
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rgbaLuma(c: AlphaColor): Int

Calculates the luminance of an ARGB color. Uses standard luminance weights for RGB components.

Name Type Description
c AlphaColor The color to analyze
Returns Description
Int Luminance value (0-255)
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rgbLuma(r: Int, g: Int, b: Int): Int

Calculates luminance from RGB components. Uses ITU-R BT.709 luma coefficients.

Name Type Description
r Int Red component (0-255)
g Int Green component (0-255)
b Int Blue component (0-255)
Returns Description
Int Luminance value (0-255)
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rgbaBlenderSrc(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

Source blend mode: Replaces backdrop with source.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The source color unchanged
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rgbaBlenderMerge(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

Merge blend mode: Blends colors based on opacity. Similar to normal blend but with different alpha handling.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The merged color
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rgbaBlenderNegBw(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderRedTint(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderBlueTint(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderNormal(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

Normal blend mode: Standard alpha compositing. This is the most common blend mode, implementing Porter-Duff "over" operator.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The composited color
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rgbaBlenderNormalDstOver(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderMultiply(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

Multiply blend mode for RGBA colors. Darkens the image by multiplying color values.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The blended color
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rgbaBlenderScreen(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderOverlay(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderDarken(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderLighten(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderColorDodge(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderColorBurn(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderHardLight(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderSoftLight(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderDifference(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderExclusion(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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lum(r: Float, g: Float, b: Float): Float

Calculates luminance using different weights than rgbLuma. Uses NTSC/PAL weights for backward compatibility.

Name Type Description
r Float Red component (0-1)
g Float Green component (0-1)
b Float Blue component (0-1)
Returns Description
Float Luminance value (0-1)
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sat(r: Float, g: Float, b: Float): Float

Calculates color saturation.

Name Type Description
r Float Red component (0-1)
g Float Green component (0-1)
b Float Blue component (0-1)
Returns Description
Float Saturation value (0-1)
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clipColor(): Void
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setLum(l: Float): Void
Name Type
l Float
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rgbaBlenderHslHue(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

HSL Hue blend mode: Uses hue from source, saturation and luminosity from backdrop.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The blended color
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rgbaBlenderHslSaturation(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderHslColor(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderHslLuminosity(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderAddition(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor

Addition blend mode: Adds color values together. Results are clamped to prevent overflow.

Name Type Description
backdrop AlphaColor The base color
src AlphaColor The source color
opacity Int Blend opacity (0-255)
Returns Description
AlphaColor The blended color
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rgbaBlenderSubtract(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor
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rgbaBlenderDivide(backdrop: AlphaColor, src: AlphaColor, opacity: Int): AlphaColor
Name Type
backdrop AlphaColor
src AlphaColor
opacity Int
Returns
AlphaColor

Private Members

ase
A_MASK: Int

Bit mask for extracting alpha channel from ARGB color.

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RGB_MASK: Int

Bit mask for extracting RGB channels from ARGB color.

ase
A_SHIFT: Int

Bit shift amount for alpha channel in ARGB format.

ase
mul_un8_0(a: Int, b: Int, t: Int): Int

Optimized 8-bit multiplication (part 1). Multiplies two 8-bit values with rounding.

Name Type Description
a Int First value (0-255)
b Int Second value (0-255)
t Int Temporary storage
Returns Description
Int Intermediate result
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mul_un8_1(t: Int): Int

Optimized 8-bit multiplication (part 2). Completes the multiplication with proper rounding.

Name Type Description
t Int Intermediate result from mul_un8_0
Returns Description
Int Final multiplied value (0-255)
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div_un8(a: Int, b: Int): Int
Name Type
a Int
b Int
Returns
Int
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setSat(s: Float): Void
Name Type
s Float