2001-01-23 Kurt Garloff <garloff@suse.de>

        * library.c, bayer.c: Enhanced the light
	  processing even more.


git-svn-id: https://svn.code.sf.net/p/gphoto/code/trunk/libgphoto2@3995 67ed7778-7388-44ab-90cf-0a291f65f57c

1 files changed, 107 insertions, 43 deletions

diff --git a/camlibs/stv0680/bayer.c b/camlibs/stv0680/bayer.c
index 6ab07d1e7..2c98e4e17 100644
--- a/camlibs/stv0680/bayer.c
+++ b/camlibs/stv0680/bayer.c
@@ -49,40 +49,96 @@ void bayer_unshuffle_preview(int w, int h, int scale, unsigned char *raw, unsign
 
 /****** gamma correction from trans[], plus hardcoded white balance */
 /* Thanks to Alexander Schwartx <alexander.schwartx@gmx.net> for this code.
-   Gamma correction (trans[] values generated by (pow((i-17)/256, GAMMA)*255)
-   where GAMMA=0.5, 1<i<255.  */
+   Gamma correction (trans[] values generated by (pow((i-17)/239, GAMMA)*254)
+   where GAMMA=0.5x, 1<i<255.  */
+/* KG: Looking at very dark parts of images, the sensor seems to produce 
+ * only very few points below 0x11 and almost none below 14. Therefore we map everything
+ * below 14 to 0 and ev'thing below 17 to 1; then the power function reigns.
+ */
+
+#define ZERO0 14 //  0--13 mapped to 0
+#define ZERO1 17 // 14--16 mapped to 1
+
+typedef struct _rgbgamma {
+	float ampl, gamma;
+} rgbgamma;
 
-#define GAMMA 0.540
-#define ZERO 16.0
 
-void light_enhance(int vw, int vh, int coarse, int fine, unsigned char *output)
+/* KG: Some notes on these:
+ * - Try to avoid strong deviations from 1.00 for the amplification,
+ *   because this potentially results in not using the full range
+ *   of colours (<1) or in clipping (>1) multiple colours to max,
+ *   which would be a loss of information.
+ * - The gamma mainly determines how fast values increase after ZERO1.
+ *   Influence on the highlights is small; therefore the description
+ *   with amplifiaction and gamma seems not very appropriate; a better
+ *   correction function would allow to influence the slope for small
+ *   and for large values indepentently without incurring loss of
+ *   accuracy/information. It should not be hard to construct such a
+ *   thing. (Splines or Bézier or Triginometric/Hyperbolic functions
+ *   could be used, e.g.)
+ * - The below parameters have been found by lots of experiments with
+ *   pictures taken at different light levels. They're optimized for
+ *   my PenCam (and my screens), of course. No theory behind this;
+ *   I don't have insight into the physics of the imaging sensor.
+ *   CCDs are linear, basically; but higher order effects may play
+ *   a role as well as the electronics that controls the shutter
+ *   and the one doing the readout.
+ */
+rgbgamma gampar[6][3] = {
+	{ { 1.02, 0.56 }, { 1.00, 0.61 }, { 0.99, 0.65 } }, // cold
+	{ { 1.01, 0.56 }, { 1.00, 0.58 }, { 1.00, 0.61 } }, // coldish
+	{ { 1.00, 0.55 }, { 1.00, 0.57 }, { 1.00, 0.59 } }, // mid
+	{ { 1.00, 0.55 }, { 1.00, 0.56 }, { 1.01, 0.55 } }, // warmish
+	{ { 1.01, 0.56 }, { 0.99, 0.57 }, { 1.03, 0.50 } }, // warm
+	{ { 1.03, 0.52 }, { 0.97, 0.57 }, { 1.04, 0.49 } }  // warm bright
+};
+
+void light_enhance(int vw, int vh, int coarse, int fine, 
+		   unsigned char avg_pix, unsigned char *output)
 {
     unsigned long int i;
     int lt=3; /* 3 is auto */
-    float wb[3][3];
-    double x, y;
-    unsigned int trans[258], v;    
-    int tmp1, tmp2, tmp3, whitex=20, whitey=20, j, k;
+    //float wb[3][3];
+    unsigned char trans[3][256];
+    unsigned char col;
+    //int tmp1, tmp2, tmp3, whitex=20, whitey=20, j, k;
 
-    double brightness = 1.0; /* FIXME: configurable? */
-    
-    /*fprintf(stderr, "(FineExp=%i CoarseExp=%i => filter=", fine, coarse); */
+    double brightness = 1.00; /* FIXME: configurable? */
+	
+    //fprintf(stderr, "(FineExp=%i CoarseExp=%i => filter=", fine, coarse);
 
+#if 0   
     if (fine >= (coarse<<1)) {
 	lt = 0;
-	/*fprintf(stderr, "natural)\n");*/
+	//fprintf(stderr, "natural)\n");
     } else if (((fine<<1) < coarse) && (coarse < 400)) {
 	lt = 2;
-	/*fprintf(stderr, "incandescent)\n");*/
+	//fprintf(stderr, "incandescent)\n");
     } else {
 	lt = 1;
-	/*fprintf(stderr, "fluorescent)\n");*/
+	//fprintf(stderr, "fluorescent)\n");
     }
-    x = brightness;
-    wb[0][0] = 1.08 * x;  wb[0][1] = 1.00 * x;  wb[0][2] = 0.95 * x;
-    wb[1][0] = 1.05 * x;  wb[1][1] = 1.00 * x;  wb[1][2] = 1.00 * x;
-    wb[2][0] = 0.90 * x;  wb[2][1] = 1.00 * x;  wb[2][2] = 1.10 * x;
+    wb[0][0] = 1.08 * x;  wb[0][1] = 1.00 * x;  wb[0][2] = 0.95 * x; // natural
+    wb[1][0] = 1.00 * x;  wb[1][1] = 1.00 * x;  wb[1][2] = 1.00 * x; // flourescent
+    wb[2][0] = 0.90 * x;  wb[2][1] = 1.00 * x;  wb[2][2] = 1.11 * x; // incandescent
+#else
+    if (fine > coarse) {
+	lt = 0; //fprintf (stderr, "cold)\n");
+    } else if (coarse < 100) {	    
+	lt = 1; //fprintf (stderr, "coldish)\n");
+    } else if (coarse < 200) {
+	lt = 2; //fprintf (stderr, "mid)\n");
+    } else if (coarse < 400) {
+	lt = 3; //fprintf (stderr, "warmish)\n");
+    } else if (avg_pix < 94) {
+	lt = 4; //fprintf (stderr, "warm)\n");
+    } else {
+	lt = 5; //fprintf (stderr, "warm, bright)\n");
+    }
+#endif
 	    
+#if 0
     /* find white pixel */
     for (j=0;j<vh;j++)
     {
@@ -92,41 +148,49 @@ void light_enhance(int vw, int vh, int coarse, int fine, unsigned char *output)
 	    tmp1 = abs(*(output+i) - *(output+i+1)); 
 	    tmp2 = abs(*(output+i) - *(output+i+2)); 
 	    tmp3 = abs(*(output+i+1) - *(output+i+2));
-	    if ((tmp1<20) && (tmp2<20) && (tmp3<20) && (*(output+i)>100)) {
+	    if ((tmp1<16) && (tmp2<16) && (tmp3<16) && (*(output+i)>=160)) {
 		whitex = k;  whitey = j;
 		break;
 	    }
 	}
     }
-    
-    for(i=1; i<256; ++i)
-    {
-	x=i; x -= ZERO;
-	if (x<1.0)
-	    x = 1.0;
-	y = pow((x/256.0),GAMMA)*255.0; 	
-	trans[i] = (unsigned int) y;
+#endif
+
+    for (col = 0; col < 3; col++) {
+	double y;
+	rgbgamma *gp = gampar[lt] + col;
+	for(i=0; i<256; ++i) {
+		if (i < ZERO0)
+			y = 0;
+		else if (i < ZERO1)
+			y = 1;
+		else 
+			y = brightness * gp->ampl * (2 + pow((i-ZERO1)/((double)254-ZERO1),gp->gamma) * 253.5);
+		if (y > 255.0)
+			y = 255.0;
+		trans[col][i] = (unsigned char) y;
+	}
     }
-    trans[0] = 0;
 
     for (i=0;i<(vw*vh*3);i+=3)
-    {   /* this (adjusting white) isn't quite right yet, so I turned it off */
-	if ( (abs(*(output+i)-*(output+i+1))<1) &&  
-	     (abs(*(output+i)-*(output+i+2))<1) &&
-	     (abs(*(output+i+1)-*(output+i+2))<1)) {
-    		y = trans[*(output+i)]*wb[lt][1]; v = (unsigned int)y;
-		v = (v > 255) ? 255 : v;
-		*(output+i) = (unsigned char) (v);
+    {   
+	int r,g,b;
+	r = *(output+i);
+	g = *(output+i+1);
+	b = *(output+i+2);
+	/* this (adjusting white) isn't quite right yet, so I turned it off */
+	if ( 0 && (abs(r-g) < 8) &&
+	          (abs(r-b) < 8) &&
+	          (abs(b-g) < 8)) {
+		int v = trans[1][(r+b+g+1)/3];
+		*(output+i) =   (unsigned char) (v);
 		*(output+i+1) = (unsigned char) (v);
 		*(output+i+2) = (unsigned char) (v);
-//		fprintf(stdout,"Adjusting white\n");
+		fprintf(stderr,"Adjusting white\n");
 	} else {          /*  this is OK  */
-		y = trans[*(output+i)]*wb[lt][0]; v = (unsigned int)y;
-		*(output+i) = (unsigned char) (v > 255) ? 255 : v;
-		y = trans[*(output+i+1)]*wb[lt][1]; v = (unsigned int)y;
-		*(output+i+1) = (unsigned char) (v > 255) ? 255 : v;
-		y = trans[*(output+i+2)]*wb[lt][2]; v = (unsigned int)y;
-		*(output+i+2) = (unsigned char) (v > 255) ? 255 : v;
+		*(output+i)   = trans[0][r];
+		*(output+i+1) = trans[1][g];
+		*(output+i+2) = trans[2][b];
 	}
     }  /* for */