IG_IP_DCRaw_camera_to_sRGB_matrix

Calculates matrix for conversion from camera color space to linear sRGB colorspace, based on two known color matrices corresponding to different light conditions, and a white point.

Declaration:

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AT_ERRCOUNT ACCUAPI IG_IP_DCRaw_camera_to_sRGB_matrix_calculate( AT_INT SrcChannelCount, HIGDoubleMatrix XYZToCam1, enumIGIlluminant Illuminant1, HIGDoubleMatrix XYZToCam2, enumIGIlluminant Illuminant2, AT_DPOINT WhiteXY, HIGDoubleMatrix* lpCamToRGB );

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AT_ERRCOUNT ACCUAPI IG_IP_DCRaw_camera_to_sRGB_matrix_calculate(
        AT_INT SrcChannelCount,
        HIGDoubleMatrix XYZToCam1,      
        enumIGIlluminant Illuminant1,   
        HIGDoubleMatrix XYZToCam2,  
        enumIGIlluminant Illuminant2,   
        AT_DPOINT WhiteXY,
        HIGDoubleMatrix* lpCamToRGB
);

Arguments:

Name	Type	Description
SrcChannelCount	AT_INT	Number of channels in the camera color space.
XYZToCam1	HIGDoubleMatrix	XYZ to camera matrix under Illuminant 1.
Illuminant1	enumIGIlluminant	Illuminant 1.
XYZToCam	HIGDoubleMatrix	XYZ to camera matrix under Illuminant 2.
Illuminant2	enumIGIlluminant	Illuminant 2.
WhiteXY	AT_DPOINT	XY coordinates of camera white point.
lpCamToRGB	HIGDoubleMatrix*	Returns conversion matrix.

Return Value:

Returns the number of ImageGear errors that occurred during this function call.

Supported Raster Image Formats:

This function does not process image pixels.

Remarks:

By "linear sRGB colorspace" we assume a linear (Gamma = 1.0) RGBcolor space that uses sRGB primaries and reference white. This color space can be converted to sRGB by applying sRGB gamma correction function.

If only one color matrix is known, pass null to XYZToCam2.

Dimensions of XYZToCam1 and XYZToCam2 must be equal to (n, 3), where n is channel count of native camera color space (3 or 4). Result matrix dimensions are (3, n).

SrcChannelCount is the image channel count before conversion. The rest of the info comes from metadata, or from the end user.

Parameter	Name	DCRaw Metadata Tag	DNG Metadata Tag
HIGDoubleMatrix XYZToCam1	ColorMatrix1	IGMDTAG_ID_DCRAW_COLORMATRIX1	IGMDTAG_ID_TIF_COLOR_MATRIX1
enumIGIlluminant Illuminant1	CalibrationIlluminant1	IGMDTAG_ID_DCRAW_CALIBRATIONILLUMINANT1	IGMDTAG_ID_TIF_CALIBRATION_ILLUMINANT1
HIGDoubleMatrix XYZToCam2	ColorMatrix2	IGMDTAG_ID_DCRAW_COLORMATRIX2	IGMDTAG_ID_TIF_COLOR_MATRIX2
enumIGIlluminant Illuminant2	CalibrationIlluminant2	IGMDTAG_ID_DCRAW_CALIBRATIONILLUMINANT2	IGMDTAG_ID_TIF_CALIBRATION_ILLUMINANT2
AT_DPOINT WhiteXY	AsShotWhiteXY AsShotNeutral	N/A IGMDTAG_ID_DCRAW_ASSHOTNEUTRAL	IGMDTAG_ID_TIF_AS_SHOT_WHITEXY IGMDTAG_ID_TIF_AS_SHOT_NEUTRAL

The WhiteXY parameter can be calculated from AsShotNeutral by using IG_IP_DCRaw_white_point_calculate. Its parameters are the same as those of IG_IP_DCRaw_camera_to_sRGB_matrix_calculate, except that it takes a lpNeutralColor parameter (AsShotNeutral) and returns WhiteXY.

It can also be calculated from a user-specified color temperature by using IG_color_temperature_convert_to_XY. There are well known color temperature presets for different shooting conditions, such as Daylight, Cloudy, Tungsten, etc.

See also IG_IP_DCRaw_RGB_gamma_LUT_build.