Change PNG's img.sidecar to ^Info, make img.depth an int.

For compatibility with the upcoming OpenEXR code, img.depth is now an int.
Like OpenEXR's code, it will now also return metadata as ^Info instead of Info.

The example was updated to retrieve the metadata this way.

It regrettably does not fix: #1018. That seems to be a codegen issue in the test runner or elsewhere.

core/image/common.odin

@@ -7,7 +7,7 @@ Image :: struct {
 	width:      int,
 	height:     int,
 	channels:   int,
-	depth:      u8,
+	depth:      int,
 	pixels:     bytes.Buffer,
 	/*
 		Some image loaders/writers can return/take an optional background color.

core/image/png/example.odin

@@ -26,12 +26,12 @@ main :: proc() {
 	if err != nil {
 		fmt.printf("Trying to read PNG file %v returned %v\n", file, err);
 	} else {
-		v:  png.Info;
+		v: ^png.Info;
 		ok: bool;
 
 		fmt.printf("Image: %vx%vx%v, %v-bit.\n", img.width, img.height, img.channels, img.depth);
 
-		if v, ok = img.sidecar.(png.Info); ok {
+		if v, ok = img.sidecar.(^png.Info); ok {
 			// Handle ancillary chunks as you wish.
 			// We provide helper functions for a few types.
 			for c in v.chunks {
@@ -195,7 +195,7 @@ write_image_as_ppm :: proc(filename: string, image: ^image.Image) -> (success: b
 	defer close(fd);
 
 	write_string(fd,
-		fmt.tprintf("P6\n%v %v\n%v\n", width, height, (1 << depth -1)),
+		fmt.tprintf("P6\n%v %v\n%v\n", width, height, (1 << uint(depth) - 1)),
 	);
 
 	if channels == 3 {

core/image/png/png.odin

@@ -392,7 +392,10 @@ load_from_stream :: proc(stream: io.Stream, options := Options{}, allocator := c
 		img = new(Image);
 	}
 
-	img.sidecar = nil;
+	info: ^Info;
+	if img.sidecar == nil {
+		info = new(Info);
+	}
 
 	ctx := &compress.Context{
 		input = stream,
@@ -413,7 +416,8 @@ load_from_stream :: proc(stream: io.Stream, options := Options{}, allocator := c
 	e:      io.Error;
 
 	header:	IHDR;
-	info:   Info;
+
+	img.sidecar = info;
 	info.chunks.allocator = context.temp_allocator;
 
 	// State to ensure correct chunk ordering.
@@ -462,12 +466,12 @@ load_from_stream :: proc(stream: io.Stream, options := Options{}, allocator := c
 				// Color image without a palette
 				img.channels = 3;
 				final_image_channels = 3;
-				img.depth    = header.bit_depth;
+				img.depth    = int(header.bit_depth);
 			} else {
 				// Grayscale
 				img.channels = 1;
 				final_image_channels = 1;
-				img.depth    = header.bit_depth;
+				img.depth    = int(header.bit_depth);
 			}
 
 			if .Alpha in header.color_type {
@@ -522,7 +526,6 @@ load_from_stream :: proc(stream: io.Stream, options := Options{}, allocator := c
 			// If we only want image metadata and don't want the pixel data, we can early out.
 			if .return_metadata not_in options && .do_not_decompress_image in options {
 				img.channels = final_image_channels;
-				img.sidecar = info;
 				return img, nil;
 			}
 			// There must be at least 1 IDAT, contiguous if more.