PNG: Inform inflate about expected output size for extra speed.

core/image/png/png.odin

@@ -668,19 +668,13 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 		return img, E_PNG.IDAT_Missing;
 	}
 
-	buf: bytes.Buffer;
-	zlib_error := zlib.inflate(idat, &buf);
-	defer bytes.buffer_destroy(&buf);
-
-	if zlib_error != nil {
-		return {}, zlib_error;
-	} else {
 	/*
-			Let's calcalate the expected size of the IDAT based on its dimensions,
+		Calculate the expected output size, to help `inflate` make better decisions about the output buffer.
-			and whether or not it's interlaced
+		We'll also use it to check the returned buffer size is what we expected it to be.
+
+		Let's calcalate the expected size of the IDAT based on its dimensions, and whether or not it's interlaced.
 	*/
 	expected_size: int;
-		buf_len := len(buf.buf);
 
 	if header.interlace_method != .Adam7 {
 		expected_size = compute_buffer_size(int(header.width), int(header.height), int(img.channels), int(header.bit_depth), 1);
@@ -698,10 +692,18 @@ load_from_context :: proc(ctx: ^$C, options := Options{}, allocator := context.a
 		}
 	}
 
+	buf: bytes.Buffer;
+	zlib_error := zlib.inflate(idat, &buf, false, expected_size);
+	defer bytes.buffer_destroy(&buf);
+
+	if zlib_error != nil {
+		return {}, zlib_error;
+	}
+
+	buf_len := len(buf.buf);
 	if expected_size != buf_len {
 		return {}, E_PNG.IDAT_Corrupt;
 	}
-	}
 
 	/*
 		Defilter just cares about the raw number of image channels present.