Add ability to crop noise from start and end of an image

README.md

@@ -39,7 +39,7 @@ To manually set the output filename
 
 Decode all WAV files in the current directory and put them in `images`
 ```sh
-./aptdec -d images *.wav
+mkdir images && ./aptdec -d images *.wav
 ```
 
 Apply a denoise filter (see [Post-Processing Effects](#post-processing-effects) for a full list of post-processing effects)
@@ -90,6 +90,7 @@ Apply a falsecolor palette
  - `d`: Denoise
  - `p`: Precipitation overlay
  - `f`: Flip image (for southbound passes)
+ - `c`: Crop noise from ends of image
 
 ## Realtime decoding
 
@@ -116,4 +117,4 @@ Environmental Satellite Receiving Stations](https://noaasis.noaa.gov/NOAASIS/pub
 
 ## License
 
-See `LICENSE`
+See `LICENSE`

common.h

@@ -32,7 +32,7 @@ typedef struct {
 typedef struct {
 	float *prow[MAX_HEIGHT]; // Row buffers
 	int nrow; // Number of rows
-	int zenith;
+	int zenith; // Row in image where satellite reaches peak elevation
 	int chA, chB; // ID of each channel
 	char name[256]; // Stripped filename
 	char *palette; // Filename of palette
@@ -64,5 +64,6 @@ enum effects {
 	Denoise='d',
 	Precipitation_Overlay='p',
 	Flip_Image='f',
-	Linear_Equalise='l'
-};
+	Linear_Equalise='l',
+	Crop_Noise='c'
+};

image.c

@@ -318,6 +318,54 @@ void flipImage(image_t *img, int width, int offset){
 	}
 }
 
+// Calculate crop to reomve noise from the start and end of an image
+void cropNoise(image_t *img){
+	#define NOISE_THRESH 150.0
+
+	// Average value of minute marker
+	float spc_rows[MAX_HEIGHT] = { 0.0 };
+	int startCrop = 0; int endCrop = img->nrow;
+	for(int y = 0; y < img->nrow; y++) {
+		for(int x = 0; x < SPC_WIDTH; x++) {
+			spc_rows[y] += img->prow[y][x + (CHB_OFFSET - SPC_WIDTH)];
+		}
+		spc_rows[y] /= SPC_WIDTH;
+
+		// Skip minute markings
+		if(spc_rows[y] < 10) {
+			spc_rows[y] = spc_rows[y-1];
+		}
+	}
+
+	// 3 row average
+	for(int y = 0; y < img->nrow; y++){
+		spc_rows[y] = (spc_rows[y+1] + spc_rows[y+2] + spc_rows[y+3])/3;
+		//img.prow[y][0] = spc_rows[y];
+	}
+
+	// Find ends
+	for(int y = 0; y < img->nrow-1; y++) {
+		if(spc_rows[y] > NOISE_THRESH){
+			endCrop = y;
+		}
+	}
+	for(int y = img->nrow; y > 0; y--) {
+		if(spc_rows[y] > NOISE_THRESH) {
+			startCrop = y;
+		}
+	}
+
+	//printf("Crop rows: %i -> %i\n", startCrop, endCrop);
+
+	// Remove the noisy rows at start
+	for(int y = 0; y < img->nrow-startCrop; y++) {
+		memmove(img->prow[y], img->prow[y+startCrop], sizeof(float)*2150);
+	}
+
+	// Ignore the noisy rows at the end
+	img->nrow = (endCrop - startCrop);
+}
+
 // --- Temperature Calibration --- //
 #include "satcal.h"
 

main.c

@@ -49,6 +49,7 @@ extern void temperature(options_t *opts, image_t *img, int offset, int width);
 extern void denoise(float **prow, int nrow, int offset, int width);
 extern void distrib(options_t *opts, image_t *img, char chid);
 extern void flipImage(image_t *img, int width, int offset);
+extern void cropNoise(image_t *img);
 
 // Palettes
 extern char GviPalette[256*3];
@@ -144,7 +145,7 @@ static int processAudio(char *filename, options_t *opts){
 	char path[256], extension[32];
 	strcpy(path, filename);
 	strcpy(path, dirname(path));
-	sscanf(basename(filename), "%[^.].%s", img.name, extension);
+	sscanf(basename(filename), "%255[^.].%31s", img.name, extension);
 
 	if(opts->realtime){
 		// Set output filename to current time when in realtime mode
@@ -205,6 +206,11 @@ static int processAudio(char *filename, options_t *opts){
 	printf("Channel A: %s (%s)\n", ch.id[img.chA], ch.name[img.chA]);
 	printf("Channel B: %s (%s)\n", ch.id[img.chB], ch.name[img.chB]);
 
+	// Crop noise from start and end of image
+	if(CONTAINS(opts->effects, Crop_Noise)){
+		cropNoise(&img);
+	}
+
 	// Denoise
 	if(CONTAINS(opts->effects, Denoise)){
 		denoise(img.prow, img.nrow, CHA_OFFSET, CH_WIDTH);
@@ -318,7 +324,7 @@ static void usage(void) {
 	fprintf(stderr,
 	"Aptdec [options] audio files ...\n"
 	"Options:\n"
-    " -i [r|a|b|t|m|p] Output image\n"
+	" -i [r|a|b|t|m|p] Output image\n"
 	"    r: Raw\n"
 	"    a: Channel A\n"
 	"    b: Channel B\n"
@@ -332,11 +338,12 @@ static void usage(void) {
 	"    p: Precipitation\n"
 	"    f: Flip image\n"
 	"    l: Linear equalise\n"
-    " -o <path>        Output filename\n"
+	"    c: Crop noise\n"
+	" -o <path>        Output filename\n"
 	" -d <path>        Image destination directory.\n"
 	" -s [15-19]       Satellite number\n"
 	" -m <path>        Map file\n"
-    " -p <path>        Path to palette\n"
+	" -p <path>        Path to palette\n"
 	" -r               Realtime decode\n"
 	" -g               Gamma adjustment (1.0 = off)\n"
 	"\nRefer to the README for more infomation\n");

pngio.c

@@ -350,12 +350,13 @@ int ImageOut(options_t *opts, image_t *img, int offset, int width, char *desc, c
 			case Denoise: break;
 			case Histogram_Equalise: break;
 			case Linear_Equalise: break;
+			case Crop_Noise: break;
 			default:
 				fprintf(stderr, "NOTICE: Unrecognised effect, \"%c\"\n", opts->effects[i]);
 				break;
 		}
 	}
-	
+
 	if(opts->map != NULL && opts->map[0] != '\0'){
 		greyscale = 0;
 	}