Discrete transfer effect

Use the discrete transfer effect to map the color intensities of an image using a step transfer function created from a list of values you provide.

The CLSID for this effect is CLSID_D2D1DiscreteTransfer.

• Example image
• Effect properties
• Requirements
• Related topics

Example image

The image here shows the input and output of the discrete transfer effect.

Before
After

ComPtr<ID2D1Effect> discreteTransferEffect;
m_d2dContext->CreateEffect(CLSID_D2D1DiscreteTransfer, &discreteTransferEffect);

discreteTransferEffect->SetInput(0, bitmap);

float table[3] = {0.0f, 0.5f, 1.0f};
discreteTransferEffect->SetValue(D2D1_DISCRETETRANSFER_PROP_RED_TABLE, table);
discreteTransferEffect->SetValue(D2D1_DISCRETETRANSFER_PROP_GREEN_TABLE, table);
discreteTransferEffect->SetValue(D2D1_DISCRETETRANSFER_PROP_BLUE_TABLE, table);

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

The transfer function is based on the list of inputs: V=(V0,V1,V2,V3,V? ,V_N) where N is the number of elements - 1.

The input pixel intensity is represented as C. The output pixel intensity, C is calculated with the equation:

For a value C, pick a value k, such that:

The output C can be calculated using the equation: C' = V?

This effect works on straight and premultiplied alpha images. The effect outputs premultiplied alpha bitmaps.

Here is what the graph of discrete transfer function looks like if the inputs are [0.25, 0.5, 0.75, 1.0].

Effect properties

Note

The values of all channels of the discrete transfer properties are unitless and have a minimum of 0.0 and a maximum 1.0.

Display name and index enumeration	Type and default value	Description
RedTable D2D1_DISCRETETRANSFER_PROP_RED_TABLE	FLOAT[] {0.0f, 1.0f}	The list of values used to define the transfer function for the Red channel.
RedDisable D2D1_DISCRETETRANSFER_PROP_RED_DISABLE	BOOL FALSE	If you set this to TRUE the effect does not apply the transfer function to the Red channel. If you set this to FALSE the effect applies the RedDiscreteTransfer function to the Red channel.
GreenTable D2D1_DISCRETETRANSFER_PROP_GREEN_TABLE	FLOAT[] {0.0f, 1.0f}	The list of values that define the transfer function for the Green channel.
GreenDisable D2D1_DISCRETETRANSFER_PROP_GREEN_DISABLE	BOOL FALSE	If you set this to TRUE the effect does not apply the transfer function to the Green channel. If you set this to FALSE the effect applies the GreenDiscreteTransfer function to the Green channel.
BlueTable D2D1_DISCRETETRANSFER_PROP_BLUE_TABLE	FLOAT[] {0.0f, 1.0f}	The list of values that define the transfer function for the Blue channel.
BlueDisable D2D1_DISCRETETRANSFER_PROP_BLUE_DISABLE	BOOL FALSE	If you set this to TRUE the effect does not apply the transfer function to the Blue channel. If you set this to FALSE the effect applies the BlueDiscreteTransfer function to the Blue channel.
AlphaTable D2D1_DISCRETETRANSFER_PROP_ALPHA_TABLE	FLOAT[] {0.0f, 1.0f}	The list of values that define the transfer function for the Alpha channel.
AlphaDisable D2D1_DISCRETETRANSFER_PROP_ALPHA_DISABLE	BOOL FALSE	If you set this to TRUE the effect does not apply the transfer function to the Alpha channel. If you set this to FALSE the effect applies the AlphaDiscreteTransfer function to the Alpha channel.
ClampOutput D2D1_DISCRETETRANSFER_PROP_CLAMP_OUTPUT	BOOL FALSE	Whether the effect clamps color values to between 0 and 1 before the effect passes the values to the next effect in the graph. The effect clamps the values before it premultiplies the alpha. If you set this to TRUE the effect will clamp the values. If you set this to FALSE, the effect will not clamp the color values, but other effects and the output surface may clamp the values if they are not of high enough precision.

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