Add histogram equalisation

Also made some floating-point math more explicit

README.md

@@ -65,9 +65,9 @@ Satellite number
 For temperature calibration
 Default: "19"
 
--e [c|t]
+-e [c|t|h]
 Enhancements
-Contrast (c) or Crop Telemetry (t)
+Contrast calibration (c), Histogram equalise (h), Crop Telemetry (t)
 Defaults: "ct"
 
 -c <file>
@@ -77,7 +77,7 @@ Default: Internal defaults
 
 ## Output
 
-Generated images are outputted in PNG, 8 bit greyscale for raw and channel A|B images, 24 bit RGB for false color.
+Generated images are outputted in PNG, 8 bit greyscale for raw and channel A|B images, palleted images for temperature and GVI false color, 24 bit RGB for false color.
 
 Image names are `audiofile-x.png`, where `x` is:
 
@@ -87,10 +87,11 @@ Image names are `audiofile-x.png`, where `x` is:
  - `t` for temperature calibrated images
  - `l` for layered images
 
-Currently there are 2 available enchancements:
+Currently there are 3 available enhancements:
 
  - `c` for contrast equalise, on by default
  - `t` for crop telemetry, on by default, only has effects on raw images
+ - `h` for histogram equalise, make the darkest color black and the brightest white
 
 ## Example
 

dsp.c

@@ -213,7 +213,7 @@ int getpixelrow(float *pixelv) {
     static float pixels[PixelLine + SyncFilterLen];
     static int npv;
     static int synced = 0;
-    static double max = 0;
+    static double max = 0.0;
 
     double corr, ecorr, lcorr;
     int res;

fcolor.c

@@ -83,7 +83,7 @@ rgba composite(rgba top, rgba bottom){
 
 void falsecolor(float vis, float temp, float *r, float *g, float *b){
     rgba buffer;
-    fcinfo.Land.a = 0; fcinfo.Sea.a = 0;
+    fcinfo.Land.a = 0.0f; fcinfo.Sea.a = 0.0f;
 
     // Calculate intensity of sea and land
     fcinfo.Sea.a  = CLIP(vis, 0, 20)/fcinfo.Seaintensity + fcinfo.Seaoffset;
@@ -91,7 +91,7 @@ void falsecolor(float vis, float temp, float *r, float *g, float *b){
 
     // Composite land on top of sea
 	buffer = composite(fcinfo.Land, fcinfo.Sea);
-    buffer.a = 1;
+    buffer.a = 1.0f;
 
     // Composite clouds on top
 	fcinfo.Cloud.a = CLIP(temp-fcinfo.Cloudthreshold, 0, fcinfo.Cloudintensity)/fcinfo.Cloudintensity;

image.c

@@ -56,6 +56,33 @@ static double tele[16];
 static double Cs;
 static int nbtele;
 
+void histogramEqualise(float **prow, int nrow, int offset, int width){
+	// Plot histogram
+	int histogram[256] = { 0 };
+	for(int y = 0; y < nrow; y++)
+		for(int x = 0; x < width; x++)
+			histogram[(int)floor(prow[y][x+offset])]++;
+
+	// Find min/max points
+	int min = -1, max = -1;
+	for(int i = 5; i < 250; i++){
+		if(histogram[i]/width/(nrow/255.0) > 1.0){
+			if(min == -1) min = i;
+			max = i;
+		}
+	}
+
+	//printf("Min Value: %i, Max Value %i\n", min, max);
+
+	// Spread values to avoid overshoot
+	min -= 5; max += 5;
+
+	// Stretch the brightness into the new range
+	for(int y = 0; y < nrow; y++)
+		for(int x = 0; x < width; x++)
+			prow[y][x+offset] = (prow[y][x+offset]-min) / (max-min) * 255;
+}
+
 // Brightness equalise, including telemetry
 void equalise(float **prow, int nrow, int offset, int width, int telestart, rgparam regr[30]){
 	offset -= SYNC_WIDTH+SPC_WIDTH;
@@ -100,7 +127,7 @@ void equalise(float **prow, int nrow, int offset, int width, int telestart, rgpa
 
 // Get telemetry data for thermal calibration/equalization
 int calibrate(float **prow, int nrow, int offset, int width, int contrastEqualise) {
-    double teleline[3000];
+    double teleline[3000] = { 0.0 };
     double wedge[16];
     rgparam regr[30];
     int n, k;
@@ -112,7 +139,6 @@ int calibrate(float **prow, int nrow, int offset, int width, int contrastEqualis
 		float *pixelv = prow[n];
 
 		// Average the center 40px
-		teleline[n] = 0.0;
 		for (int i = 3; i < 43; i++) teleline[n] += pixelv[i + offset + width];
 		teleline[n] /= 40.0;
     }
@@ -127,7 +153,7 @@ int calibrate(float **prow, int nrow, int offset, int width, int contrastEqualis
 	 * difference in brightness, this will always be in the center of
 	 * the frame and can thus be used to find the start of the frame
 	 */
-	float max = 0;
+	double max = 0.0;
     for (n = nrow / 3 - 64; n < 2 * nrow / 3 - 64; n++) {
 		float df;
 

main.c

@@ -177,9 +177,9 @@ static int ImageOut(char *filename, char *chid, float **prow, int nrow, int widt
 			}else if(effects == 3){
 				// Layered image, overlay clouds in channel B over channel A
 				float cloud = CLIP(pixelv[i+CHB_OFFSET]-141, 0, 255)/114;
-				pixel[i] = MCOMPOSITE(255, cloud, pixelv[i+CHA_OFFSET], 1);
+				pixel[i] = MCOMPOSITE(240, cloud, pixelv[i+CHA_OFFSET], 1);
 			}else{
-				pixel[i] = pixelv[i + offset + f];
+				pixel[i] = CLIP(pixelv[i + offset + f], 0, 255);
 			}
 		}
 
@@ -228,6 +228,7 @@ static void distrib(char *filename, float **prow, int nrow) {
 }
 
 extern int calibrate(float **prow, int nrow, int offset, int width, int contrastEqualise);
+extern void histogramEqualise(float **prow, int nrow, int offset, int width);
 extern void temperature(float **prow, int nrow, int ch, int offset);
 extern int Ngvi(float **prow, int nrow);
 extern void readfcconf(char *file);
@@ -243,6 +244,7 @@ static void usage(void) {
 	" -e [c|t]       Enhancements\n"
 	"     c: Contrast equalise\n"
 	"     t: Crop telemetry\n"
+	"     h: Histogram equalise\n"
 	" -i [r|a|b|c|t] Output image type\n"
 	"     r: Raw\n"
 	"     a: Channel A\n"
@@ -350,7 +352,6 @@ int main(int argc, char **argv) {
 			if (getpixelrow(prow[nrow]) == 0)
 				break;
 
-
 			printf("Row: %d\r", nrow);
 			fflush(stdout);
 		}
@@ -358,9 +359,6 @@ int main(int argc, char **argv) {
 
 		sf_close(inwav);
 
-		// Layered & false color images both need brightness equalization
-		int contrastEqualise = CONTAINS(enchancements, 'c') || CONTAINS(imgopt, 'l') || CONTAINS(imgopt, 'c');
-
 		chA = calibrate(prow, nrow, CHA_OFFSET, CH_WIDTH, 0);
 		chB = calibrate(prow, nrow, CHB_OFFSET, CH_WIDTH, 0);
 		printf("Channel A: %s (%s)\n", ch.id[chA], ch.name[chA]);
@@ -374,9 +372,15 @@ int main(int argc, char **argv) {
 		}
 
 		// Run the contrast equalise here because the temperature calibration requires raw data
-		if(contrastEqualise)
+		// Also layered & false color images both need brightness equalization
+		if(CONTAINS(enchancements, 'c') || CONTAINS(enchancements, 'h') || CONTAINS(imgopt, 'l') || CONTAINS(imgopt, 'c'))
 			calibrate(prow, nrow, CHA_OFFSET, CH_WIDTH+TELE_WIDTH+SYNC_WIDTH+SPC_WIDTH+CH_WIDTH, 1);
 
+		if(CONTAINS(enchancements, 'h')){
+			histogramEqualise(prow, nrow, CHA_OFFSET, CH_WIDTH);
+			histogramEqualise(prow, nrow, CHB_OFFSET, CH_WIDTH);
+		}
+
 		// Layered
 		if (CONTAINS(imgopt, 'l')){
 			if(chA == 1){