1 files changed, 45 insertions, 0 deletions
diff --git a/unvignette.c b/unvignette.c
new file mode 100644
index 0000000..36e30e7
--- /dev/null
+++ b/unvignette.c
@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <cairo.h>
+
+#define CLAMP(x, l, h) (((x) > (h)) ? (h) : (((x) < (l)) ? (l) : (x)))
+
+static inline double
+cos4(double x)
+{
+	return CLAMP(pow(cos(x), 4.0), 0.001, 1.0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	cairo_surface_t *s;
+	unsigned char *row, *p;
+	int x, y, i, width, height, stride;
+
+	if (argc < 2)
+		exit(EXIT_FAILURE);
+
+	s = cairo_image_surface_create_from_png(argv[1]);
+	if (!s || cairo_surface_status(s) != CAIRO_STATUS_SUCCESS)
+		exit(EXIT_FAILURE);
+
+	row    = cairo_image_surface_get_data(s);
+	width  = cairo_image_surface_get_width(s);
+	height = cairo_image_surface_get_height(s);
+	stride = cairo_image_surface_get_stride(s);
+
+	for (y = 0; y < height; ++y, row += stride) {
+		for (x = 0, p = row; x < width; ++x, p += 4) {
+			double c = 1.0 / cos4(1.2 * (x - width / 2) / width);
+			for (i = 0; i < 3; ++i)
+				p[i] = CLAMP(c * p[i], 0, 255);
+		}
+	}
+
+	cairo_surface_write_to_png(s, argc > 2 ? argv[2] : "unvignetted.png");
+	cairo_surface_destroy(s);
+
+	return 0;
+}