void DirectXTileRenderer::UpdateWhiteLevelScale()

in cpp/AdvancedColorImages/AdvancedColorImages/DirectXTileRenderer.cpp [300:333]

• 23 lines of code
• 4 McCabe index (conditional complexity)

void DirectXTileRenderer::UpdateWhiteLevelScale(float brightnessAdjustment, float sdrWhiteLevel)
{
	float scale = 1.0f;

	switch (m_imageInfo.imageKind)
	{
	case AdvancedColorKind::HighDynamicRange:
		// HDR content should not be compensated by the SdrWhiteLevel parameter.
		scale = 1.0f;
		break;

	case AdvancedColorKind::StandardDynamicRange:
	case AdvancedColorKind::WideColorGamut:
	default:
		scale = sdrWhiteLevel / sc_nominalRefWhite;
		break;
	}

	// The user may want to manually adjust brightness specifically for this image, on top of any
	// white level adjustment for SDR/WCG content. Brightness adjustment using a linear gamma scale
	// is mainly useful for HDR displays, but can be useful for HDR content tonemapped to an SDR/WCG display.
	scale *= brightnessAdjustment;

	// SDR white level scaling is performing by multiplying RGB color values in linear gamma.
	// We implement this with a Direct2D matrix effect.
	D2D1_MATRIX_5X4_F matrix = D2D1::Matrix5x4F(
		scale, 0, 0, 0,  // [R] Multiply each color channel
		0, scale, 0, 0,  // [G] by the scale factor in 
		0, 0, scale, 0,  // [B] linear gamma space.
		0, 0, 0, 1,  // [A] Preserve alpha values.
		0, 0, 0, 0); //     No offset.

	check_hresult(m_whiteScaleEffect->SetValue(D2D1_COLORMATRIX_PROP_COLOR_MATRIX, matrix));
}