impRGBtoW(3) Impressario impRGBtoW(3)NAME
impRGBtoW, impWtoRGB, impRGBtoK, impKtoRGB, impRGBtoCMY, impCMYtoRGB,
impRGBtoYIQ, impYIQtoRGB, impRGBtoYUV, impYUVtoRGB, impRGBtoYCbCr,
impYCbCrtoRGB, impRGBtoCMYK, impRGBtoDevCMYK, impCMYKtoRGB, impRGBtoHSV,
impHSVtoRGB, impRGBtoHLS, impHLStoRGB - color space conversion
SYNOPSIS
#include <imp.h>
W Conversions:
void impRGBtoW(short *rbuf, short *gbuf, short *bbuf,
short *wbuf, int n);
void impWtoRGB(short *wbuf, short *rbuf, short *gbuf,
short *bbuf, int n);
K Conversions:
void impRGBtoK(short *rbuf, short *gbuf, short *bbuf,
short *kbuf, short unity, int n);
void impKtoRGB(short *kbuf, short *rbuf, short *gbuf,
short *bbuf, short unity, int n);
CMY Conversions:
void impRGBtoCMY(short *rbuf, short *gbuf, short *bbuf,
short *cbuf, short *mbuf, short *ybuf,
short unity, int n);
void impCMYtoRGB(short *cbuf, short *mbuf, short *ybuf,
short *rbuf, short *gbuf, short *bbuf,
short unity, int n);
YIQ Conversions:
void impRGBtoYIQ(short *rbuf, short *gbuf, short *bbuf,
short *ybuf, short *ibuf, short *qbuf,
int n);
void impYIQtoRGB(short *ybuf, short *ibuf, short *qbuf,
short *rbuf, short *gbuf, short *bbuf,
int n);
YUV Conversions:
void impRGBtoYUV(short *rbuf, short *gbuf, short *bbuf,
short *ybuf, short *ubuf, short *vbuf,
int n);
void impYUVtoRGB(short *ybuf, short *ubuf, short *vbuf,
Page 1
impRGBtoW(3) Impressario impRGBtoW(3)
short *rbuf, short *gbuf, short *bbuf,
int n);
YCbCr Conversions:
void impRGBtoYCbCr(short *rbuf, short *gbuf, short *bbuf,
short *ybuf, short *cbbuf, short *crbuf,
int n);
void impYCbCrtoRGB(short *ybuf, short *cbbuf, short *crbuf,
short *rbuf, short *gbuf, short *bbuf,
int n);
CMYK Conversions:
void impRGBtoCMYK(short *rbuf, short *gbuf, short *bbuf,
short *cbuf, short *mbuf, short *ybug,
short *kbuf, short unity, int n);
void impRGBtoDevCMYK(short *rbuf, short *gbuf, short *bbuf,
short *cbuf, short *mbuf, short *ybug,
short *kbuf, IMPUCRFunc ucr, IMPBGFunc bg,
short unity, int n);
short (*IMPBGFunc)(short k);
short (*IMPUCRFunc)(short k);
void impCMYKtoRGB(short *cbuf, short *mbuf, short *ybuf,
short *kbuf, short *rbuf, short *gbug,
short *bbuf, short unity, int n);
HSV Conversions:
void impRGBtoHSV(short *rbuf, short *gbuf, short *bbuf,
float *hbuf, float *sbuf, float *vbuf,
int n);
void impHSVtoRGB(float *hbuf, float *sbuf, float *vbuf,
short *rbuf, short *gbuf, short *bbuf,
int n);
HLS Conversions:
void impRGBtoHLS(short *rbuf, short *gbuf, short *bbuf,
float *hbuf, float *lbuf, float *sbuf,
short unity, int n);
void impHLStoRGB(float *hbuf, float *lbuf, float *sbuf,
short *rbuf, short *gbuf, short *bbuf,
short unity, int n);
Page 2
impRGBtoW(3) Impressario impRGBtoW(3)DESCRIPTION
The functions described here perform color space conversion between a
given color space and RGB. The actual transformations performed are
described below. Certain functions specify the parameter unity. unity
should be set to the value of maximum possible intensity for the arrays
specified. For example, if eight bit data is being converted, unity would
be specified as 255. If the data makes use of the full sixteen bits
available in each array element, unity would be specified as 65535. Note
that the parameter n specifies the number of elements in the arrays and
not the number of bytes.
W Conversions:
R
W = | 0.299 0.587 0.114 | * G
B
|
|
R W
G = W
B W
|
|
|
|
K Conversions:
1.0 - R
K = | 0.299 0.587 0.114 | * 1.0 - G
1.0 - B
|
|
R 1.0 - K
G = 1.0 - K
B 1.0 - K
|
|
|
|
CMY Conversions:
C 1.0 - R
M = 1.0 - G
Y 1.0 - B
|
|
|
|
R 1.0 - C
G = 1.0 - M
B 1.0 - Y
|
|
|
|
YIQ Conversions:
Y 0.299 0.587 0.114 R
I = 0.596 -0.274 -0.322 * G
Q 0.212 -0.523 0.311 B
|
|
|
|
|
|
R 1.000 0.955 0.622 Y
G = 1.000 -0.271 -0.648 * I
B 1.000 -1.107 1.702 Q
|
|
|
|
|
|
Page 3
impRGBtoW(3) Impressario impRGBtoW(3)
|
|
|
|
|
|
YUV Conversions:
Y 0.299 0.587 0.114 R
U = -0.147 -0.289 0.436 * G
V 0.615 -0.515-0.100 B
|
|
|
|
|
|
R 1.000 0.000 1.140 Y
G = 1.000 -0.395 -0.581 * U
B 1.000 2.032 0.000 V
|
|
|
|
|
|
YCbCr Conversions:
Y 0.299 0.587 0.114 R
Cb = -0.169-0.331 0.500 * G
Cr 0.500 -0.419-0.081 B
|
|
|
|
|
|
R 1.000 -0.001 1.402 Y
G = 1.000 -0.344 -0.714 * Cb
B 1.000 1.772 0.001 Cr
|
|
|
|
|
|
CMYK Conversions:
Ci = 1.0 - R
Mi = 1.0 - G
Yi = 1.0 - B
K = Min(Ci, Mi, Yi)
C = Ci - K
M = Mi - K
Y = Yi - K
Ci = 1.0 - R
Mi = 1.0 - G
Yi = 1.0 - B
Ki = Min(Ci, Mi, Yi)
Kucr = UCR(Ki)
Device C = Min(1.0, Max(0.0, Ci - Kucr))
Device M = Min(1.0, Max(0.0, Mi - Kucr))
Device Y = Min(1.0, Max(0.0, Yi - Kucr))
Device K = BG(Ki)
Ci = C + K
Mi = M + K
Yi = Y + K
R = 1.0 - Min(1.0, Ci)
G = 1.0 - Min(1.0, Mi)
B = 1.0 - Min(1.0, Yi)
For HSV conversions refer to Computer Graphics, Principals and Practice,
Foley and Van Dam, 2nd. Edition, pp. 590-592.
Page 4
impRGBtoW(3) Impressario impRGBtoW(3)
For HLS conversions refer to the citing above pp. 592-595.
NOTE
It is the caller's responsibility to allocate all buffer storage.
SEE ALSOlibimp(3)
Page 5
