add basic image manipulation functions

meson.build

@@ -9,7 +9,9 @@ project(
 )
 
 sources = [
+  'src/image.c',
   'src/main.c',
+  'src/ppm.c',
 ]
 
 executable(

src/image.c

@@ -0,0 +1,20 @@
+#include "image.h"
+
+#include <stdlib.h>
+
+struct image *create_image(size_t w, size_t h) {
+    // FIXME: not checking for overflow
+    struct image *i = malloc(w * h * sizeof(*i->buf) + sizeof(*i));
+
+    if (!i)
+        return NULL;
+
+    i->w = w;
+    i->h = h;
+
+    return i;
+}
+
+void destroy_image(struct image *image) {
+    free(image);
+}

src/image.h

@@ -0,0 +1,19 @@
+#ifndef IMAGE_H
+#define IMAGE_H
+
+#include <stddef.h>
+
+struct image {
+    size_t w;
+    size_t h;
+    struct pixel {
+        unsigned char r;
+        unsigned char g;
+        unsigned char b;
+    } buf[];
+};
+
+struct image *create_image(size_t w, size_t h);
+void destroy_image(struct image *image);
+
+#endif /* !IMAGE_H */

src/main.c

@@ -1,3 +1,6 @@
+#include "image.h"
+#include "ppm.h"
+
 int main(void) {
     return 0;
 }

src/ppm.c

@@ -0,0 +1,22 @@
+#include "ppm.h"
+
+#include <stdio.h>
+#include "image.h"
+
+void print_ppm(const struct image *image, FILE *f) {
+    // Header
+    fputs("P3\n", f);
+    fprintf(f, "%zu %zu\n", image->w, image->h);
+    fputs("255\n", f);
+
+    // One row per line
+    for (size_t i = 0; i < image->h; ++i) {
+        for (size_t j = 0; j < image->w; ++j) {
+            if (j != 0)
+                fputc(' ', f);
+            const struct pixel *p = &image->buf[i * image->w + j];
+            fprintf(f, "%hhu %hhu %hhu", p->r, p->g, p->b);
+        }
+        fputc('\n', f);
+    }
+}

src/ppm.h

@@ -0,0 +1,10 @@
+#ifndef PPM_H
+#define PPM_H
+
+#include <stdio.h>
+
+struct image; // Forward declaration
+
+void print_ppm(const struct image *image, FILE *f);
+
+#endif /* !PPM_H */