sub & subalpha

3 files changed, 70 insertions, 4 deletions

diff --git a/main.c b/main.c
index 72c12ac..2cf7fa0 100644
--- a/main.c
+++ b/main.c
@@ -1,9 +1,10 @@
 #include "image.h"
 #include "myrand.h"
 #include <time.h>
+#include <stdlib.h>
 
 int
-main(void)
+main(int argc, char **argv)
 {
 	mysrand(time(NULL));
 
@@ -15,8 +16,10 @@ main(void)
 	kldImage_vflip(cloud);
 
 	kldImage_invert(sky);
+	const int m = (argc > 1) ? atoi(argv[1]) : 255;
+	kldImage_mod(sky, KLD_COLOR(m, m, m, 255));
 
-	kldImage_add(cloud, sky);
+	kldImage_sub(cloud, sky);
 	kldImage_writePAM(cloud, stdout);
 
 	kldImage_free(sky);
diff --git a/src/image.c b/src/image.c
index 2e57a5f..aa5024a 100644
--- a/src/image.c
+++ b/src/image.c
@@ -429,7 +429,7 @@ kldImage_bit3(KldImage *img)
 }
 
 void
-kldImage_mask(KldImage *img, KldColor mask)
+kldImage_mod(KldImage *img, KldColor mask)
 {
 	NULL_SAFETY();
 
@@ -502,3 +502,60 @@ kldImage_add(KldImage *img, KldImage *other)
 
 	return 0;
 }
+
+int
+kldImage_sub(KldImage *img, KldImage *other)
+{
+	NULL_SAFETY(-1);
+	NULL_SAFETY_EX(other, -1);
+
+	if (img->width != other->width || img->height != other->height) {
+		log_error("img (%lu x %lu) and other (%lu x %lu) "
+		          "dims don't match",
+		          img->width, img->height, other->width, other->height);
+		return -1;
+	}
+
+	for (size_t i = 0; i < img->size; i++) {
+		const KldColor c0 = img->data[i];
+		const KldColor c1 = other->data[i];
+		const int r = KLD_COLOR_R(c0) - KLD_COLOR_R(c1);
+		const int g = KLD_COLOR_G(c0) - KLD_COLOR_G(c1);
+		const int b = KLD_COLOR_B(c0) - KLD_COLOR_B(c1);
+		img->data[i] = KLD_COLOR(
+		    (r < 0) ? 0 : r,
+		    (g < 0) ? 0 : g,
+		    (b < 0) ? 0 : b,
+		    KLD_COLOR_A(c0)
+		);
+	}
+
+	return 0;
+}
+
+int
+kldImage_subalpha(KldImage *img, KldImage *other)
+{
+	NULL_SAFETY(-1);
+	NULL_SAFETY_EX(other, -1);
+
+	if (img->width != other->width || img->height != other->height) {
+		log_error("img (%lu x %lu) and other (%lu x %lu) "
+		          "dims don't match",
+		          img->width, img->height, other->width, other->height);
+		return -1;
+	}
+
+	for (size_t i = 0; i < img->size; i++) {
+		const KldColor c0 = img->data[i];
+		const int a = KLD_COLOR_A(c0) - KLD_COLOR_A(other->data[i]);
+		img->data[i] = KLD_COLOR(
+		    KLD_COLOR_R(c0),
+		    KLD_COLOR_G(c0),
+		    KLD_COLOR_B(c0),
+		    (a < 0) ? 0 : a
+		);
+	}
+
+	return 0;
+}
diff --git a/src/image.h b/src/image.h
index fbc8442..2c6b453 100644
--- a/src/image.h
+++ b/src/image.h
@@ -51,10 +51,16 @@ void kldImage_chaos3(KldImage *img);
 
 void kldImage_bit3(KldImage *img);
 
-void kldImage_mask(KldImage *img, KldColor mask);
+void kldImage_mod(KldImage *img, KldColor mask);
 
 /* return -1 if sizes are not equal */
 int kldImage_blend(KldImage *img, KldImage *other, float ratio);
 
 /* return -1 if sizes are not equal */
 int kldImage_add(KldImage *img, KldImage *other);
+
+/* return -1 if sizes are not equal; ignores alpha */
+int kldImage_sub(KldImage *img, KldImage *other);
+
+/* return -1 if sizes are not equal */
+int kldImage_subalpha(KldImage *img, KldImage *other);