GR32.Blend.Modes.PhotoShop

Description

The GR32.Blend.Modes.PhotoShop unit implements the full suite of standard Adobe Photoshop and W3C Compositing and Blending Specification blending algorithms for Graphics32.

Overview of Photoshop Blend Modes

Unlike Porter-Duff operators, which primarily determine geometry-based alpha coverage cutouts and layer intersections, Photoshop blend modes blend color channel values ( $C_{S}$ foreground/source and $C_{B}$ background/backdrop) according to non-linear color algebra and component-based color space transformations.

The blend modes in GR32.Blend.Modes.PhotoShop are organized into 5 functional groups:

Group	Description
Darken	Always produce a result color that is at least as dark as either constituent color.
Lighten	Always produce a result color that is at least as light as either constituent color.
Contrast	Increase or decrease contrast based on whether the source color component is lighter or darker than 50% neutral gray.
Inversion	Highlight differences or invert colors between source and backdrop layers.
Component	Blend color attributes based on Hue, Saturation, and Luminosity (Luminance).

Luminance & Lightness Functions

The unit includes cross-platform inline helper routines to compute lightness, luminance, brightness, and average intensity values from 32-bit TColor32 values or RGB byte components:

Routine	Formula / Standard	Description
`ColorLightness`	$\frac{max (R, G, B) + min (R, G, B)}{2}$	Calculates HSL lightness (Chroma midpoint).
`ColorLuminance`	$0.30 R + 0.59 G + 0.11 B$	Calculates perceived Rec. 601 NTSC luminance (Luma).
`ColorAverage`	$\frac{R + G + B}{3}$	Calculates unweighted average RGB intensity.
`ColorBrightness`	$max (R, G, B)$	Calculates HSV Value (maximum color component).

Summary Table

Darken group

ID	Name	Class	Formula / Behavior
`Darken`	Darken	`TGraphics32BlenderDarken`	$B \leq F ? B : F$
`multiply`	Multiply	`TGraphics32BlenderMultiply`	$\frac{B \cdot F}{255}$
`ColorBurn`	Color Burn	`TGraphics32BlenderColorBurn`	$255 - \frac{(255 - B) \cdot 255}{F}$
`LinearBurn`	Linear Burn	`TGraphics32BlenderLinearBurn`	$max (0, B + F - 255)$
`Darker`	Darker Color	`TGraphics32BlenderDarkerColor`	Compares overall luminance; retains darker pixel.

Lighten group

ID	Name	Class	Formula / Behavior
`Lighten`	Lighten	`TGraphics32BlenderLighten`	$B \geq F ? B : F$
`screen`	Screen	`TGraphics32BlenderScreen`	$255 - \frac{(255 - B) (255 - F)}{255}$
`ColorDodge`	Color Dodge	`TGraphics32BlenderColorDodge`	$min (255, \frac{B \cdot 255}{255 - F})$
`Add`	Linear Dodge (Add)	`TGraphics32BlenderLinearDodge`	$min (255, B + F)$
`Lighter`	Lighter Color	`TGraphics32BlenderLighterColor`	Compares overall luminance; retains lighter pixel.

Contrast group

ID	Name	Class	Formula / Behavior
`Overlay`	Overlay	`TGraphics32BlenderOverlay`	Screens or multiplies based on backdrop $B$ .
`SoftLight`	Soft Light	`TGraphics32BlenderSoftLight`	Diffused spotlight effect based on source $F$ .
`HardLight`	Hard Light	`TGraphics32BlenderHardLight`	Harsh spotlight effect based on source $F$ .
`VividLight`	Vivid Light	`TGraphics32BlenderVividLight`	Dodges or burns by adjusting contrast.
`LinearLight`	Linear Light	`TGraphics32BlenderLinearLight`	Dodges or burns by adjusting brightness.
`PinLight`	Pin Light	`TGraphics32BlenderPinLight`	Replaces color depending on 50% gray threshold.
`HardMix`	Hard Mix	`TGraphics32BlenderHardMix`	Thresholds channels to 0 or 255 primary colors.

Inversion group

ID	Name	Class	Formula / Behavior
`Difference`	Difference	`TGraphics32BlenderDifference`	$\| B - F \|$
`Exclusion`	Exclusion	`TGraphics32BlenderExclusion`	$F + B - \frac{2 \cdot F \cdot B}{255}$
`Negation`	Negation	`TGraphics32BlenderNegation`	$255 - \| B - F \|$

Component group

ID	Name	Class	Formula / Behavior
`Hue`	Hue	`TGraphics32BlenderHue`	Combines source Hue with backdrop Saturation and Luminance.
`Saturation`	Saturation	`TGraphics32BlenderSaturation`	Combines source Saturation with backdrop Hue and Luminance.
`Color`	Color	`TGraphics32BlenderColor`	Combines source Hue and Saturation with backdrop Luminance.
`Luminosity`	Luminosity	`TGraphics32BlenderLuminance`	Combines source Luminance with backdrop Hue and Saturation.

Darken Blend Modes

Darken

ID: Darken
Name: Darken
Class: TGraphics32BlenderDarken

Compares each channel value of the source and backdrop color and selects the smaller (darker) of the two values.

Multiply

ID: multiply
Name: Multiply
Class: TGraphics32BlenderMultiply

Multiplies the source and backdrop color values. The result is always a darker color. Blending with white leaves the image unchanged; blending with black produces black.

Color Burn

ID: ColorBurn
Name: Color Burn
Class: TGraphics32BlenderColorBurn

Darkens the backdrop color to reflect the source color by increasing the contrast between the two. Painting with white produces no change.

Linear Burn

ID: LinearBurn
Name: Linear Burn
Class: TGraphics32BlenderLinearBurn

Darkens the backdrop color to reflect the source color by decreasing brightness. Painting with white produces no change. Also known as the Subtract blend mode.

Darker Color

ID: Darker
Name: Darker color
Class: TGraphics32BlenderDarkerColor

Compares the overall perceived luminance of the source and backdrop pixels and displays the lower-luminance color in its entirety.

Lighten Blend Modes

Lighten

ID: Lighten
Name: Lighten
Class: TGraphics32BlenderLighten

Compares each channel value of the source and backdrop color and selects the larger (lighter) of the two values.

Screen

ID: screen
Name: Screen
Class: TGraphics32BlenderScreen

Multiplies the inverse of the source and backdrop colors, then complements the result. The result color is always lighter. Screening with black leaves the color unchanged; screening with white yields white.

Color Dodge

ID: ColorDodge
Name: Color Dodge
Class: TGraphics32BlenderColorDodge

Brightens the backdrop color to reflect the source color by decreasing contrast between them. Painting with black produces no change.

Linear Dodge (Add)

ID: Add
Name: Linear Dodge (Add)
Class: TGraphics32BlenderLinearDodge

Sums the channel values of the backdrop and source colors. Blending with black causes no change; blending with white yields pure white.

Lighter Color

ID: Lighter
Name: Lighter color
Class: TGraphics32BlenderLighterColor

Compares the overall perceived luminance of the source and backdrop pixels and displays the higher-luminance color in its entirety.

Contrast Blend Modes

Overlay

ID: Overlay
Name: Overlay
Class: TGraphics32BlenderOverlay

Multiplies or screens the colors depending on the backdrop color value. Patterns or colors overlay the existing backdrop while preserving its highlights and shadows.

Soft Light

ID: SoftLight
Name: Soft Light
Class: TGraphics32BlenderSoftLight

Darkens or lightens colors depending on the source color value. The visual effect is similar to shining a diffused spotlight on the backdrop image.

Hard Light

ID: HardLight
Name: Hard Light
Class: TGraphics32BlenderHardLight

Multiplies or screens colors depending on the source color value. The visual effect is similar to shining a harsh spotlight on the backdrop image.

Vivid Light

ID: VividLight
Name: Vivid Light
Class: TGraphics32BlenderVividLight

Burns or dodges colors by increasing or decreasing contrast depending on whether the source color is darker or lighter than 50% gray.

Linear Light

ID: LinearLight
Name: Linear Light
Class: TGraphics32BlenderLinearLight

Burns or dodges colors by increasing or decreasing brightness depending on whether the source color is darker or lighter than 50% gray.

Pin Light

ID: PinLight
Name: Pin Light
Class: TGraphics32BlenderPinLight

Replaces colors depending on the source color. If the source is lighter than 50% gray, darker backdrop pixels are replaced; if darker than 50% gray, lighter backdrop pixels are replaced.

Hard Mix

ID: HardMix
Name: Hard Mix
Class: TGraphics32BlenderHardMix

Adds the red, green, and blue channel values of the source to the backdrop. Values $\geq 255$ become 255, and values $< 255$ become 0, reducing all pixels to primary additive colors (Red, Green, Blue, White, Black).

Inversion Blend Modes

Difference

ID: Difference
Name: Difference
Class: TGraphics32BlenderDifference

Subtracts the darker of the source and backdrop colors from the lighter color. Blending with white inverts backdrop colors; blending with black produces no change.

Exclusion

ID: Exclusion
Name: Exclusion
Class: TGraphics32BlenderExclusion

Creates an effect similar to Difference mode but lower in contrast. Blending with white inverts base color values; blending with black produces no change.

Negation

ID: Negation
Name: Negation
Class: TGraphics32BlenderNegation

Subtracts the darker color from the lighter color and complements the result. Blending with black inverts backdrop colors; blending with white produces no change.

Component (HSL) Blend Modes

Hue

ID: Hue
Name: Hue
Class: TGraphics32BlenderHue

Creates a result color with the luminance and saturation of the backdrop color and the hue of the source color.

Saturation

ID: Saturation
Name: Saturation
Class: TGraphics32BlenderSaturation

Creates a result color with the luminance and hue of the backdrop color and the saturation of the source color.

Color

ID: Color
Name: Color
Class: TGraphics32BlenderColor

Creates a result color with the luminance of the backdrop color and the hue and saturation of the source color. Preserves gray levels and is useful for tinting monochrome or color images.

Luminosity

ID: Luminosity
Name: Luminosity
Class: TGraphics32BlenderLuminance

Creates a result color with the hue and saturation of the backdrop color and the luminance of the source color. This mode creates the inverse effect of the Color blend mode.

Description ​

Overview of Photoshop Blend Modes ​

Luminance & Lightness Functions ​

Summary Table ​

Darken group ​

Lighten group ​

Contrast group ​

Inversion group ​

Component group ​

Darken Blend Modes ​

Darken ​

Multiply ​

Color Burn ​

Linear Burn ​

Darker Color ​

Lighten Blend Modes ​

Lighten ​

Screen ​

Color Dodge ​

Linear Dodge (Add) ​

Lighter Color ​

Contrast Blend Modes ​

Overlay ​

Soft Light ​

Hard Light ​

Vivid Light ​

Linear Light ​

Pin Light ​

Hard Mix ​

Inversion Blend Modes ​

Difference ​

Exclusion ​

Negation ​

Component (HSL) Blend Modes ​

Hue ​

Saturation ​

Color ​

Luminosity ​

See also ​