--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Makefile	Fri Jun 13 14:18:52 2008 +0200
@@ -0,0 +1,2 @@
+resize-gd: resize-gd.c
+	gcc -o resize-gd -lgd -lpng -lz -ljpeg  -lm resize-gd.c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/resize-gd.c	Fri Jun 13 14:18:52 2008 +0200
@@ -0,0 +1,76 @@
+/* compile with: gcc -lgd -lpng -lz -ljpeg  -lm resize-gd.c  */
+
+#include <stdio.h>
+#include <stdlib.h>  /* for atoi() */
+#include <string.h>
+#include "gd.h" /* Bring in the gd library functions */
+
+
+enum {
+	Png,
+	Jpg,
+};
+
+
+int main(int argc, char* argv[]) {
+	int i;
+	int w, h;
+	int x, y;
+	int type;
+	gdImagePtr im_in;
+	gdImagePtr im_out;
+	FILE* in;
+	FILE* out;
+
+	if (argc < 3) {
+		puts("usage: resize-gd <width>x<height> <imagefiles>");
+		exit(1);
+	}
+
+	/* parse width and height */
+	w = atoi(argv[1]);
+	h = atoi(strstr(argv[1], "x") + 1);
+	printf("w: %d  h: %d\n", w, h);
+
+	/* process images */
+	for (i = 2; i < argc; i++) {
+		printf("processing file '%s'\n", argv[i]);
+
+		if (strcmp(&(argv[i][strlen(argv[i])-4]), ".png") == 0) {
+			type = Png;
+		} else if (strcmp(&(argv[i][strlen(argv[i])-4]), ".jpg") == 0) {
+			type = Jpg;
+		} else {
+			fprintf(stderr, "unknown filetype\n");
+			exit(2);
+		}
+
+		/* Load a large png to shrink in the smaller one */
+		in = fopen(argv[i], "rb");
+		if (type == Png) {
+			im_in = gdImageCreateFromPng(in);
+		} else if (type == Jpg) {
+			im_in = gdImageCreateFromJpeg(in);
+		}
+		fclose(in);
+
+		im_out = gdImageCreateTrueColor(w, h);
+
+		/* Now copy the large image */
+		gdImageCopyResampled(im_out, im_in, 0, 0, 0, 0, im_out->sx, im_out->sy, im_in->sx, im_in->sy);
+
+		/* write out */
+		out = fopen(argv[i], "wb");
+		if (type == Png) {
+			gdImagePng(im_out, out);
+		} else if (type == Jpg) {
+			gdImageJpeg(im_out, out, -1);
+		}
+		fclose(out);
+
+		gdImageDestroy(im_in);
+		gdImageDestroy(im_out);
+	}
+
+	return 0;
+}