ppm: simple example to generate a ppm image

3 files changed, 81 insertions, 0 deletions

diff --git a/ppm/Makefile b/ppm/Makefile
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index 0000000..031bfc6
--- /dev/null
+++ b/ppm/Makefile
@@ -0,0 +1,8 @@
+main: main.zig ppm.zig
+	zig run main.zig
+
+show:
+	nsxiv test.ppm
+
+clean:
+	$(RM) test.ppm
diff --git a/ppm/main.zig b/ppm/main.zig
new file mode 100644
index 0000000..6e1bb1b
--- /dev/null
+++ b/ppm/main.zig
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+const std = @import("std");
+const ppm = @import("ppm.zig");
+
+pub fn main() !void {
+    var img = ppm.ppm(200, 200).init;
+    defer img.dump("test.ppm") catch unreachable;
+
+    for (img.row(10)) |*px| {
+        px.*.r = 255;
+    }
+    for (img.row(20)) |*px| {
+        px.*.g = 255;
+    }
+    for (img.row(30)) |*px| {
+        px.*.b = 255;
+    }
+
+    const white = ppm.Pixel{ .r = 255, .g = 255, .b = 255 };
+
+    img.set(100, 100, white);
+    img.set(199, 199, white);
+}
diff --git a/ppm/ppm.zig b/ppm/ppm.zig
new file mode 100644
index 0000000..0606a8b
--- /dev/null
+++ b/ppm/ppm.zig
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+const std = @import("std");
+const assert = std.debug.assert;
+
+pub const Pixel = extern struct {
+    r: u8,
+    g: u8,
+    b: u8,
+};
+
+pub fn ppm(comptime xdim: u32, comptime ydim: u32) type {
+    return struct {
+        const Self = @This();
+
+        /// Pixel data of the ppm image.
+        px: [ydim][xdim]Pixel,
+
+        /// Initial value of the `ppm` type.
+        pub const init: Self = .{
+            .px = undefined,
+        };
+
+        /// Set pixel data at `(x, y)`.
+        pub fn set(self: *Self, x: u32, y: u32, px: Pixel) void {
+            assert(x < xdim and y < ydim);
+            self.px[y][x] = px;
+        }
+
+        /// Get slice of pixels for row `y`.
+        pub fn row(self: *Self, y: u32) []Pixel {
+            assert(y < ydim);
+            return self.px[y][0..];
+        }
+
+        /// Write out image file with `name`.
+        pub fn dump(self: *const Self, name: []const u8) !void {
+            const f = try std.fs.cwd().createFile(name, .{ .truncate = true });
+            defer f.close();
+
+            const w = f.writer();
+            // Write ppm header (in ascii):
+            //  MAGIC XDIM YDIM MAX_COLOR_VALUE
+            try w.print("P6 {} {} 255\n", .{ xdim, ydim });
+
+            for (self.px) |curr_row| {
+                for (curr_row) |px| {
+                    try w.writeStruct(px);
+                }
+            }
+        }
+    };
+}