Gamma transfer effect

Use the gamma transfer effect to map the color intensities of an image using a gamma function created using an amplitude, exponent, and offset you provide for each channel.

The CLSID for this effect is CLSID_D2D1GammaTransfer. To use this effect, add dxguid.lib to the linker dependencies.

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

Example image

Before
After

ComPtr<ID2D1Effect> gammaTransferEffect;
m_d2dContext->CreateEffect(CLSID_D2D1GammaTransfer, &gammaTransferEffect);

gammaTransferEffect->SetInput(0, bitmap);

gammaTransferEffect->SetValue(D2D1_GAMMATRANSFER_PROP_RED_EXPONENT, 0.25f);
gammaTransferEffect->SetValue(D2D1_GAMMATRANSFER_PROP_GREEN_EXPONENT, 0.25f);
gammaTransferEffect->SetValue(D2D1_GAMMATRANSFER_PROP_BLUE_EXPONENT, 0.25f);

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

This effect applies a gamma transfer function based on the equation here.

The input pixel intensity is represented as C and the output pixel intensity as C'. C' = Amplitude * C^Exponent + Offset

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

Effect properties

Note

For all channels of the gamma transfer properties:

• The amplitude value is not bounded and is unitless.
• The exponent value is not bounded and is unitless.
• The offset value is not bounded and is unitless.

Display name and index enumeration	Description
RedAmplitude D2D1_GAMMATRANSFER_PROP_RED_AMPLITUDE	The amplitude of the gamma transfer function for the Red channel. The type is FLOAT. The default value is 1.0f.
RedExponent D2D1_GAMMATRANSFER_PROP_RED_EXPONENT	The exponent of the gamma transfer function for the Red channel. The type is FLOAT. The default value is 1.0f.
RedOffset D2D1_GAMMATRANSFER_PROP_RED_OFFSET	The offset of the gamma transfer function for the Red channel. The type is FLOAT. The default value is 0.0f.
RedDisable D2D1_GAMMATRANSFER_PROP_RED_DISABLE	If you set this to TRUE it does not apply the transfer function to the Red channel. An identity transfer function is used. If you set this to FALSE it applies the gamma transfer function to the Red channel. The type is BOOL. The default value is FALSE.
GreenAmplitude D2D1_GAMMATRANSFER_PROP_GREEN_AMPLITUDE	The amplitude of the gamma transfer function for the Green channel. The type is FLOAT. The default value is 1.0f.
GreenExponent D2D1_GAMMATRANSFER_PROP_GREEN_EXPONENT	The exponent of the gamma transfer function for the Green channel. The type is FLOAT. The default value is 1.0f.
GreenOffset D2D1_GAMMATRANSFER_PROP_GREEN_OFFSET	The offset of the gamma transfer function for the Green channel. The type is FLOAT. The default value is 0.0f.
GreenDisable D2D1_GAMMATRANSFER_PROP_GREEN_DISABLE	If you set this to TRUE it does not apply the transfer function to the Green channel. An identity transfer function is used. If you set this to FALSE it applies the gamma transfer function to the Green channel. The type is BOOL. The default value is FALSE.
BlueAmplitude D2D1_GAMMATRANSFER_PROP_BLUE_AMPLITUDE	The amplitude of the gamma transfer function for the Blue channel. The type is FLOAT. The default value is 1.0f.
BlueExponent D2D1_GAMMATRANSFER_PROP_BLUE_EXPONENT	The exponent of the gamma transfer function for the Blue channel. The type is FLOAT. The default value is 1.0f.
BlueOffset D2D1_GAMMATRANSFER_PROP_BLUE_OFFSET	The offset of the gamma transfer function for the Blue channel. The type is FLOAT. The default value is 0.0f.
BlueDisable D2D1_GAMMATRANSFER_PROP_BLUE_DISABLE	If you set this to TRUE it does not apply the transfer function to the Blue channel. An identity transfer function is used. If you set this to FALSE it applies the gamma transfer function to the Blue channel. The type is BOOL. The default value is FALSE.
AlphaAmplitude D2D1_GAMMATRANSFER_PROP_ALPHA_AMPLITUDE	The amplitude of the gamma transfer function for the alpha channel. The type is FLOAT. The default value is 1.0f.
AlphaExponent D2D1_GAMMATRANSFER_PROP_ALPHA_EXPONENT	The exponent of the gamma transfer function for the alpha channel. The type is FLOAT. The default value is 1.0f.
AlphaOffset D2D1_GAMMATRANSFER_PROP_ALPHA_OFFSET	The offset of the gamma transfer function for the alpha channel. The type is FLOAT. The default value is 0.0f.
AlphaDisable D2D1_GAMMATRANSFER_PROP_ALPHA_DISABLE	If you set this to TRUE it does not apply the transfer function to the alpha channel. An identity transfer function is used. If you set this to FALSE it applies the gamma transfer function to the alpha channel. The type is BOOL. The default value is FALSE.
ClampOutput D2D1_GAMMATRANSFER_PROP_CLAMP_OUTPUT	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. The type is BOOL. The default value is FALSE.

Output bitmap

The output bitmap size is the same as the input bitmap size.

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