From 39529749bd4df513541bf259795ee6698f4fd679 Mon Sep 17 00:00:00 2001
From: Patrick Roth <roth@stettbacher.ch>
Date: Thu, 1 Jul 2021 10:54:34 +0200
Subject: change weights to -100.0...+100.0 per cent

The upper and lower horizontal trapeze line will change.
The vertical weight is not implemented now!
---
 trapcorr.c | 55 +++++++++++++++++++++++++++++--------------------------
 1 file changed, 29 insertions(+), 26 deletions(-)

(limited to 'trapcorr.c')

diff --git a/trapcorr.c b/trapcorr.c
index 3ace25f..aef2411 100644
--- a/trapcorr.c
+++ b/trapcorr.c
@@ -188,7 +188,6 @@ static void correct(struct trapcorr_data_t *data) {
 	const int scale_fact = data->map_scale_fact;
 	const int is_color = data->is_color;
 	
-	
 	for(y = 0; y < height; y++) {
 		for(x = 0; x < width; x++) {
 			x_corr = map->x;
@@ -228,15 +227,32 @@ static void init_map(struct trapcorr_data_t *data) {
 	const int scale_fact = (1 << (data->map_scale_fact));
 	const int width = data->width;
 	const int height = data->height;
-	const float p = data->wh * (width/2.0f);
-	float p_i, row_scale, x_corr, y_corr;
+	float p, p_i, row_scale, x_corr, y_corr;
 	int x_start, x_end;
+	int shrink_upper;
 	
+	// convert -100.0...+100.0 ---> 0.0...2.0
+	const float fact = data->wh/100.0f+1.0f;
 	
-// 	printf("XXX P = %f\n", p);
+	/*
+	 * Checking whether we shrink upper or lower horizontal
+	 * trapeze line.
+	 */ 
+	if(data->wh <= 1.0f) {
+		// upper line shrinks
+		shrink_upper = 1;
+		p = fact * (width/2.0f);
+	}
+	else {
+		// lower line shrinks
+		shrink_upper = 0;
+		p = (2.0f - fact) * (width/2.0f);
+	}
 	
 	/*
-	 * horizontal correction
+	 * We'll loop through image with y-axis symmetrically centered.
+	 * So the image is horizontally shifted to left. Do calculate
+	 * the start and end values on x-axis.
 	 */ 
 	if((width%2) == 0) {
 		// even width
@@ -249,11 +265,15 @@ static void init_map(struct trapcorr_data_t *data) {
 		x_end = (width-1)/2;
 	}
 	
-// 	printf("XXX x_start = %d, x_end = %d, %d x %d\n", x_start,  x_end, width, height);
-	
+	// loop through image
 	for(y = 0; y < height; y++) {
-		
-		p_i = ((width/2.0f - p) / height) * y + p;
+		if(shrink_upper) {
+			p_i = ((width/2.0f - p) / height) * y + p;
+		}
+		else {
+			p_i = (-1.0f*((width/2.0f - p) / height)) * y + width/2.0f;
+		}
+				
 		row_scale = 2.0f * p_i / width;
 		
 		// we don't correct vertically
@@ -262,25 +282,9 @@ static void init_map(struct trapcorr_data_t *data) {
 		for(x = x_start; x <= x_end; x++) {
 			x_corr = x/row_scale;
 			
-// 			if(x > -325 && x < -315 && y < 2) {
-// 				printf("%d/%d: p_i = %f, row_scale = %f, x_corr = %f\n", y, x, p_i, row_scale, x_corr);
-// 			}
-			
 			// trapeze is horizontally symmetrically centered --> shift right
 			x_corr -= x_start;
 			
-// 			if(x > -325 && x < -315 && y < 2) {
-// 				printf("    ----> x_corr (shift)= %f\n", x_corr);
-// 			}
-			
-			// range check
-			if(x_corr < 0.0f) {
-				x_corr = 0.0f;
-			}
-			else if(x_corr > (width-1.0f)) {
-				x_corr = width-1.0f;
-			}
-			
 			// apply scaling factor
 			map->x = (int)roundf(x_corr*scale_fact);
 			map->y = (int)roundf(y_corr*scale_fact);
@@ -305,7 +309,6 @@ int trapcorr(struct trapcorr_data_t *trapcorr_data) {
 		trapcorr_data->map_scale_fact = 9;	// scale by 9 means 2^9 = 512
 		init_map(trapcorr_data);
 		trapcorr_data->map_init = 1;
-		printf("XXXXX map initialized!\n");
 	}
 	
 	// apply perspective correction
-- 
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