Convert ND image with colour information to a (n-1)D grayvalue image (in dipIO)
#include "dipio_tools.h"
dip_Error dipio_Colour2Gray ( in, out, photometric )
This function converts a colour image, as read by ImageReadColour, to a grayvalue intensity image. in is expected to contain the colour information along the last axis. out will be a scalar image with one less dimension than the input.
| Data type | Name | Description |
| dip_Image | in | Input image |
| dip_Image | out | Output image |
| dipio_PhotometricInterpretation | photometric | Photometric interpretation |
The enumerator dipio_PhotometricInterpretation contains the following constants:
| Name | Description |
| DIPIO_PHM_GREYVALUE | No colour information present; it's a grey-value image. |
| DIPIO_PHM_RGB | RGB image (the first three planes are red, green and blue) |
| DIPIO_PHM_RGB_NONLINEAR | Non-linear R'G'B' image (RGB channels to the power of 0.4) |
| DIPIO_PHM_CMY | CMY image (the first three planes are cyan, magenta and yellow) |
| DIPIO_PHM_CMYK | CMYK image (the first four planes are cyan, magenta, yellow and black) |
| DIPIO_PHM_CIELUV | CIE L*u'v' image (the first three planes are luminosity, u* and v*) |
| DIPIO_PHM_CIELAB | CIE L*a*b* image (the first three planes are luminosity, a* and b*) |
| DIPIO_PHM_CIEXYZ | CIE XYZ (the first three planes are X, Y and Z) |
| DIPIO_PHM_CIEYXY | CIE Yxy (the first three planes are Y, x and y) |
| DIPIO_PHM_HCV | HCV image (the first three planes are hue, chroma and value) |
| DIPIO_PHM_HSV | HSV image (the first three planes are hue, saturation and value) |
| DIPIO_PHM_DEFAULT | Same as DIPIO_PHM_GREYVALUE |
| DIPIO_PHM_GENERIC | Anything can be coded in the channels; the same as DIPIO_PHM_CMYK |
Most file formats support only some of these.
Some colourspaces are not converted correctly. R'G'B' (DIPIO_PHM_RGB_NONLINEAR), is treated like RGB. From a CIE Lab (DIPIO_PHM_CIELAB) or Luv (DIPIO_PHM_CIELUV) the luminosity channel is extracted, which is also a non-linear conversion away from the intensity. From HCV (DIPIO_PHM_HCV) and HSV (DIPIO_PHM_HSV) the value channel is extracted, which again is a non-linear conversion away from the intensity. CMYK (DIPIO_PHM_CMYK) and CMY (DIPIO_PHM_CMY) conversion is not implemented. Specifying these values will result in an error.
ImageRead, ImageReadColour, ImageReadROI
DIPlib on-line documentation | Function reference | Global function index