Blend effect

Use the blend effect to combine 2 images. This effect has 26 blend modes.

The CLSID for this effect is CLSID_D2D1Blend.

• Blending examples
• Effect properties
• Blend modes
• HSL color space conversions
  • Converting from RGB to HSL
  • Converting from HSL to RGB
• Output bitmap
• Sample code
• Requirements
• Related topics

Blending examples

Here is an example image of every blend mode of the blend effect. A full list of the blend modes and the corresponding mode properties are in the next section

Here is another example using the exclusion mode.

Before image 1
Before image 2
After

ComPtr<ID2D1Effect> blendEffect;
m_d2dContext->CreateEffect(CLSID_D2D1Blend, &blendEffect);

blendEffect->SetInput(0, bitmap);
blendEffect->SetInput(1, bitmapTwo);
blendEffect->SetValue(D2D1_BLEND_PROP_MODE, D2D1_BLEND_MODE_EXCLUSION);

m_d2dContext->BeginDraw();
m_d2dContext->DrawImage(blendEffect.Get());
m_d2dContext->EndDraw();

Effect properties

Display name and index enumeration	Description
Mode D2D1_BLEND_PROP_MODE	The blend mode used for the effect. See Blend modes for more info. The type is D2D1_BLEND_MODE. The default value is D2D1_BLEND_MODE_MULTIPLY.

Blend modes

The table here shows all the blend modes of this effect. The helper functions necessary to compute the output of the effect are in the next section.

Color: O_PRGB = f(F_RGB, B_RGB) * F_A * B_A + F_RGB * F_A * (1 - B_A) + B_RGB * B_A * (1 - F_A)

Alpha: O_A = F_A * (1 - B_A) + B_A

Where:

• O_PRGB is the pre-multiplied output color
• O_A is Output Alpha
• B_RGB is the un-pre-multiplied destination color
• B_A is destination alpha
• F_RGB is the un-pre-multiplied source color
• F_A is source alpha
• f(S_RGB, D_RGB) is a blend function that varies per-blend-mode

Some of the blend modes require conversion to and from the hue, saturation, luminosity (HSL) color space to RGB.

Enumeration	Equation
D2D1_BLEND_MODE_DARKEN	Basic blend formula for alpha only.
D2D1_BLEND_MODE_MULTIPLY	Basic blend formula for alpha only.
D2D1_BLEND_MODE_COLOR_BURN	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_LINEAR_BURN	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_DARKER_COLOR	Basic blend formula for alpha only.
D2D1_BLEND_MODE_LIGHTEN	Basic blend formula for alpha only.
D2D1_BLEND_MODE_SCREEN	Basic blend formula for alpha only.
D2D1_BLEND_MODE_COLOR_DODGE	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_LINEAR_DODGE	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_LIGHTER_COLOR	Basic blend formula for alpha only.
D2D1_BLEND_MODE_OVERLAY	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_SOFT_LIGHT	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_HARD_LIGHT	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_VIVID_LIGHT	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_LINEAR_LIGHT	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_PIN_LIGHT	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_HARD_MIX	Basic blend formulas with f(FRGB, BRGB) =
D2D1_BLEND_MODE_DIFFERENCE	Basic blend formulas with f(FRGB, BRGB) = abs(FRGB - BRGB)
D2D1_BLEND_MODE_EXCLUSION	Basic blend formulas with f(FRGB, BRGB) = FRGB + BRGB 2 * FRGB * BRGB
D2D1_BLEND_MODE_HUE	Basic blend formula for alpha only.
D2D1_BLEND_MODE_SATURATION	Basic blend formula for alpha only.
D2D1_BLEND_MODE_COLOR	Basic blend formula for alpha only.
D2D1_BLEND_MODE_LUMINOSITY	Basic blend formula for alpha only.
D2D1_BLEND_MODE_DISSOLVE	Given: A scene coordinate XY for the current pixel A deterministic pseudo-random number generator rand(XY) based on seed coordinate XY, with unbiased distribution of values from [0, 1]
D2D1_BLEND_MODE_SUBTRACT	Basic blend formula for alpha only.
D2D1_BLEND_MODE_DIVISION	Basic blend formula for alpha only.

Note

For all Blend modes, the output value is premultiplied and clamped to the range [0, 1].

HSL color space conversions

The luminosity component is computed using the RGB weights here:

• k_R = 0.30
• k_G = 0.59
• k_B = 0.11

Converting from RGB to HSL

This places S and L in the range [0.0, 1.0] and H in the range [-1.0, 5.0].

Converting from HSL to RGB

To convert the other way we use the inverse of the previous calculations.

If S = 0 then R = G = B = L

Otherwise there are six hue-dependant cases:

If H is greater than 0, the values are in the red/magenta sector where R > B > G.

If H is greater than or equal to 0 and less than 1, the values are in the red/yellow sector where R > G > B.

If H is greater than or equal to 1 and less than 2, the values are in the yellow/green sector where G > R > B.

If H is greater than or equal to 2 and less than 3, the values are in the green/cyan sector where G > B > R.

If H is greater than or equal to 3 and less than 4, the values are in the cyan/blue sector where B > G > R.

If H is greater than or equal to 4, the values are in the blue/magenta sector where B > R > G.

Because the blending modes make arbitrary combinations of HSL components from two different colors, it is common for the converted RGB value to be out-of-gamut, that is, one or more channel components may be outside the legal range of [0.0, 1.0]. These colors are brought back into gamut by minimally reducing the saturation, while preserving both hue and luminosity:

Output bitmap

The output bitmap for this effect is always the size of the union of the two input images.

Sample code

For an example of this effect, download the Direct2D composite effect modes sample.

Requirements

Requirement	Value
Minimum supported client	Windows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Minimum supported server	Windows 8 and Platform Update for Windows 7 [desktop apps | Windows Store apps]
Header	d2d1effects.h
Library	d2d1.lib, dxguid.lib

Related topics

ID2D1Effect