Add util to write p7 image

src/pam.c

@@ -0,0 +1,30 @@
+#include "pam.h"
+#include <stdio.h>
+#include <string.h>
+
+void write_p7_image(u64 width, u64 height, u8 *buf, const char *outfile) {
+  FILE *fp = fopen(outfile, "wb");
+  if (!fp) {
+    fprintf(stderr, "Couldn't open file: %s\n", outfile);
+    return;
+  }
+
+  char header[4096] = {0};
+  snprintf(header, 4095,
+           "P7\n"
+           "WIDTH %lu\n"
+           "HEIGHT %lu\n"
+           "DEPTH 4\n"
+           "MAXVAL 255\n"
+           "TUPLTYPE RGB_ALPHA\n"
+           "ENDHDR\n",
+           width, height);
+
+  u64 hdr_size = strlen(header);
+  u64 buf_size = width * height * 4;
+
+  fwrite(header, hdr_size, 1, fp);
+  fwrite(buf, buf_size, 1, fp);
+
+  fclose(fp);
+}

src/pam.h

@@ -0,0 +1,8 @@
+#ifndef PAM_H
+#define PAM_H
+
+#include "aliases.h"
+
+void write_p7_image(u64 width, u64 height, u8 *buf, const char *outfile);
+
+#endif // PAM_H