Arithmetic composite effect

Use the arithmetic composite effect to combine 2 images using a weighted sum of pixels from the input images.

The CLSID for this effect is CLSID_D2D1ArithmeticComposite.

• Formula
• Example image
• Effect properties
• Output bitmap
• Requirements
• Related topics

Formula

The formula here is used to compute this effect.

Output_rgba = C1 * Source_rgba * Destination_rgba + C2 * Source_rgba + C3 * Destination_rgba + C4

Where C1, C2, C3, C4 are coefficients that you set.

The coefficients map to the values in a D2D1_VECTOR_4F (x, y, z, w):

• x = C1
• y = C2
• z = C3
• w = C4

Example image

A simple example is to add the source and destination pixels. In the example, 2 rounded rectangles are composited together. The source rectangle is blue and the destination is red.

The image here is the output of the Arithmetic Composite effect with the coefficients of the equation set to the values here.

• C1 = 0
• C2 = 1
• C3 = 1
• C4 = 0

The result is that the pixel values for the source and destination are added. The regions where the rectangles don't overlap the RGBA values are all 0. Where the rectangles overlap the color is magenta because the R and B values are both at maximum.

Here's another example image with code.

Before image 1
Before image 2
After

ComPtr<ID2D1Effect> arithmeticCompositeEffect;
m_d2dContext->CreateEffect(CLSID_D2D1ArithmeticComposite, &arithmeticCompositeEffect);

arithmeticCompositeEffect->SetInput(0, bitmap);
arithmeticCompositeEffect->SetInput(1, bitmapTwo);
arithmeticCompositeEffect->SetValue(D2D1_ARITHMETICCOMPOSITE_PROP_COEFFICIENTS, D2D1::Vector4F(0.0f, 0.5f, 0.5f, 0.0f));

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

Effect properties

Output bitmap

The output bitmap depends on the coefficient values. These are the possible output bitmap sizes.

• If C1 is the only non-zero coefficient, the output size is the intersection of the input rectangles.
• If C2 is the only non-zero coefficient, the output size is the size of the Source rectangle.
• If C3 is the only non-zero coefficient, the output size is the size of the Destination rectangle..
• If all coefficients are zero, the output size is an empty rectangle.
• For all other coefficient values, the output size is the union of the input rectangles.

Requirements

Related topics

ID2D1Effect