Am 23.04.12, 11:46 +0200 schrieb marti.ma...@littlecms.com:
I think it makes complete sense. I would, however, only modify
case of pure gamma function (type 0). It happens that the spec already
defines what to do on negative parts for other types. Just try the
build-in sRGB for example, that already has this feature enabled:
transicc -i*XYZ -o *sRGB
LittleCMS ColorSpace conversion calculator - 4.1 [LittleCMS 2.04]
Enter values, 'q' to quit
X? -10
Y? -10
Z? -10
R=-350.9086 G=-332.4046 B=-424.3584
wonderful :-)
I'm adding the change to my development sources, will commit in a
week or so (I have many changes for 2.4 this time)
The attached patch covers the remaining occurences of pow in
DefaultEvalParametricFn(). However, I could not test it appropriately.
kind regards
Kai-Uwe Behrmann
--
www.oyranos.org
PS: the patch is attributed to Marti Maria and MIT licensed.
diff --git a/src/cmsgamma.c b/src/cmsgamma.c
index 02dc910..1eb127f 100644
--- a/src/cmsgamma.c
+++ b/src/cmsgamma.c
@@ -250,16 +250,24 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
// X = Y ^ Gamma
case 1:
- if (R < 0)
- Val = 0;
+ if (R < 0) {
+ if (Params[0] == 1.0)
+ Val = R;
+ else
+ Val = 0;
+ }
else
Val = pow(R, Params[0]);
break;
// Type 1 Reversed: X = Y ^1/gamma
case -1:
- if (R < 0)
- Val = 0;
+ if (R < 0) {
+ if (Params[0] == 1.0)
+ Val = R;
+ else
+ Val = 0;
+ }
else
Val = pow(R, 1/Params[0]);
break;
@@ -276,8 +284,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (e > 0)
Val = pow(e, Params[0]);
- else
- Val = 0;
+ else {
+ if (Params[0] == 1.0)
+ Val = e;
+ else
+ Val = 0;
+ }
}
else
Val = 0;
@@ -286,13 +298,14 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
// Type 2 Reversed
// X = (Y ^1/g - b) / a
case -2:
- if (R < 0)
- Val = 0;
+ if (R < 0) {
+ if (Params[0] == 1.0)
+ Val = R;
+ else
+ Val = 0;
+ }
else
Val = (pow(R, 1.0/Params[0]) - Params[2]) / Params[1];
-
- if (Val < 0)
- Val = 0;
break;
@@ -301,8 +314,6 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
// Y = c | else
case 3:
disc = -Params[2] / Params[1];
- if (disc < 0)
- disc = 0;
if (R >= disc) {
@@ -310,8 +321,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (e > 0)
Val = pow(e, Params[0]) + Params[3];
- else
- Val = 0;
+ else {
+ if (Params[0] == 1.0)
+ Val = pow(e, Params[0]) + Params[3];
+ else
+ Val = 0;
+ }
}
else
Val = Params[3];
@@ -328,8 +343,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (e > 0)
Val = (pow(e, 1/Params[0]) - Params[2]) / Params[1];
- else
- Val = 0;
+ else {
+ if (Params[0] == 1.0)
+ Val = (pow(e, 1/Params[0]) - Params[2]) / Params[1];
+ else
+ Val = 0;
+ }
}
else {
Val = -Params[2] / Params[1];
@@ -347,8 +366,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (e > 0)
Val = pow(e, Params[0]);
- else
- Val = 0;
+ else {
+ if (Params[0] == 1.0)
+ Val = e;
+ else
+ Val = 0;
+ }
}
else
Val = R * Params[3];
@@ -359,8 +382,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
// X=Y/c | Y< (ad+b)^g
case -4:
e = Params[1] * Params[4] + Params[2];
- if (e < 0)
- disc = 0;
+ if (e < 0) {
+ if (Params[0] == 1.0)
+ disc = Params[0];
+ else
+ disc = 0;
+ }
else
disc = pow(e, Params[0]);
@@ -383,8 +410,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (e > 0)
Val = pow(e, Params[0]) + Params[5];
- else
- Val = 0;
+ else {
+ if (Params[0] == 1.0)
+ Val = e + Params[5];
+ else
+ Val = 0;
+ }
}
else
Val = R*Params[3] + Params[6];
@@ -400,8 +431,12 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
if (R >= disc) {
e = R - Params[5];
- if (e < 0)
- Val = 0;
+ if (e < 0) {
+ if (Params[0] == 1.0)
+ Val = (e - Params[2]) / Params[1];
+ else
+ Val = 0;
+ }
else
Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1];
}
@@ -418,8 +453,11 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
case 6:
e = Params[1]*R + Params[2];
- if (e < 0)
- Val = 0;
+ if (e < 0) {
+ if (Params[0] == 1.0)
+ Val = e + Params[3];
+ else
+ Val = 0;
else
Val = pow(e, Params[0]) + Params[3];
break;
@@ -427,10 +465,14 @@ cmsFloat64Number DefaultEvalParametricFn(cmsInt32Number Type, const cmsFloat64Nu
// ((Y - c) ^1/Gamma - b) / a
case -6:
e = R - Params[3];
- if (e < 0)
- Val = 0;
+ if (e < 0) {
+ if (Params[0] == 1.0)
+ Val = (e - Params[2]) / Params[1];
+ else
+ Val = 0;
+ }
else
- Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1];
+ Val = (pow(e, 1.0/Params[0]) - Params[2]) / Params[1];
break;
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