1 files changed, 88 insertions, 0 deletions
diff --git a/image/png/load.ha b/image/png/load.ha
new file mode 100644
index 0000000..d3578f8
--- /dev/null
+++ b/image/png/load.ha
@@ -0,0 +1,88 @@
+use errors;
+use io;
+use memio;
+
+// A decoded PNG image.
+export type image = struct {
+	// Image header
+	ihdr: ihdr,
+	// RGBA palette data (if present, otherwise an empty slice)
+	palette: []u32,
+	// Raw pixel data
+	pixels: []u8,
+};
+
+// Reads a PNG image from an [[io::handle]], returning the decoded header,
+// palette (if present), and raw pixel data. The caller must pass the return
+// value to [[image_finish]] to discard resources associated with the image.
+export fn load(in: io::handle) (image | error) = {
+	let success = false;
+
+	const reader = newreader(in)?;
+
+	match (nextchunk(&reader)?) {
+	case io::EOF =>
+		return invalid;
+	case let ctype: u32 =>
+		if (ctype != IHDR) {
+			return invalid;
+		};
+	};
+	const ihdr = ihdr_read(&reader)?;
+	let pixels: ([]u8 | void) = void;
+	defer if (!success && pixels is []u8) free(pixels as []u8);
+	let palette: []u32 = [];
+	defer if (!success) free(palette);
+
+	for (true) match (nextchunk(&reader)?) {
+	case io::EOF =>
+		return invalid;
+	case let ctype: u32 =>
+		switch (ctype) {
+		case IHDR =>
+			return invalid;
+		case PLTE =>
+			if (len(palette) != 0) {
+				return invalid;
+			};
+			let plte = new_plte_reader(&reader)?;
+			palette = alloc([0...], plte_ncolors(&plte));
+			plte_read(&plte, palette)?;
+		case IDAT =>
+			if (pixels is []u8) {
+				return invalid;
+			};
+			let pixbuf: []u8 = alloc([0...], decoder_bufsiz(&ihdr));
+			defer free(pixbuf);
+			let idat = new_idat_reader(&reader);
+			let dec = newdecoder(&idat, &ihdr, pixbuf)?;
+			defer io::close(&dec)!;
+			pixels = io::drain(&dec)?;
+		case IEND =>
+			iend_read(&reader)?;
+			break;
+		case =>
+			if (is_critical(ctype)) {
+				return unsupported;
+			};
+			io::copy(io::empty, &reader)?;
+		};
+	};
+
+	if (pixels is void) {
+		return invalid;
+	};
+
+	success = true;
+	return image {
+		ihdr = ihdr,
+		palette = palette,
+		pixels = pixels as []u8,
+	};
+};
+
+// Frees resources associated with an [[image]].
+export fn image_finish(img: *image) void = {
+	free(img.palette);
+	free(img.pixels);
+};