Implement shaders (#1)

Reviewed-on: #1

	* Start implementing shaders and move vector code to dedicated files
	* Extract shader into its own header
	* Ensure pixel coordinates are within bounds
	* Refactor shader code and implement fragment shaders
	* Create shaders
	* Reorganise code
Co-authored-by: Abdelrahman <said.abdelrahman89@gmail.com>
Co-committed-by: Abdelrahman <said.abdelrahman89@gmail.com>

src/pam/pam.c

@@ -0,0 +1,88 @@
+#include "pam.h"
+#include "img.h"
+#include "mem_arena.h"
+#include <stddef.h>
+#include <stdint.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);
+}
+
+Image *load_p6_image(Arena *arena, const char *filename) {
+  Image *output = NULL;
+
+  if (!arena || !filename) {
+    goto RETURN_VALUE;
+  }
+
+  FILE *fp = fopen(filename, "rb");
+  if (!fp) {
+    goto RETURN_VALUE;
+  }
+
+  char type[4] = {0};
+  fread(type, 3, 1, fp);
+  if (strncmp(type, "P6\n", 4) != 0) {
+    goto CLOSE_FILE;
+  }
+
+  u64 w, h;
+  fscanf(fp, "%lu %lu\n", &w, &h);
+
+  u64 max;
+  fscanf(fp, "%lu\n", &max);
+  if (max > UINT8_MAX) {
+    goto CLOSE_FILE;
+  }
+
+  output = wapp_mem_arena_alloc(arena, sizeof(Image));
+  if (!output) {
+    goto CLOSE_FILE;
+  }
+
+  output->width = w;
+  output->height = h;
+  if (!init_buffer(arena, output)) {
+    goto CLOSE_FILE;
+  }
+
+  Colour colour = {0};
+  for (u64 y = 0; y < h; ++y) {
+    for (u64 x = 0; x < w; ++x) {
+      fread(&colour, 3, 1, fp);
+      colour.a = 255;
+      set_pixel(output, x, y, &colour);
+    }
+  }
+
+CLOSE_FILE:
+  fclose(fp);
+
+RETURN_VALUE:
+  return output;
+}

src/pam/pam.h

@@ -0,0 +1,10 @@
+#ifndef PAM_H
+#define PAM_H
+
+#include "aliases.h"
+#include "img.h"
+
+void write_p7_image(u64 width, u64 height, u8 *buf, const char *outfile);
+Image *load_p6_image(Arena *arena, const char *filename);
+
+#endif // PAM_H