Write test ppm image to stdout.

zigrtiow/src/main.zig

@@ -1,7 +1,29 @@
 const std = @import("std");
 
 pub fn main() anyerror!void {
-    std.log.info("All your codebase are belong to us.", .{});
+    const image_width: usize = 256;
+    const image_height: usize = 256;
+
+    const stdout = std.io.getStdOut();
+
+    std.log.info("Writing image {d}x{d}\n", .{ image_width, image_height });
+    try stdout.writer().print("P3\n{d} {d}\n255\n", .{ image_width, image_height });
+
+    var j: usize = 0;
+    while (j < image_height) : (j += 1) {
+        var i: usize = 0;
+        while (i < image_width) : (i += 1) {
+            var r = @intToFloat(f32, i) / @intToFloat(f32, image_width - 1);
+            var g = @intToFloat(f32, image_height - j - 1) / @intToFloat(f32, image_height - 1);
+            var b: f32 = 0.25;
+
+            var ir = @floatToInt(u8, 255.999 * r);
+            var ig = @floatToInt(u8, 255.999 * g);
+            var ib = @floatToInt(u8, 255.999 * b);
+
+            try stdout.writer().print("{d} {d} {d}\n", .{ ir, ig, ib });
+        }
+    }
 }
 
 test "basic test" {