icns

commit 05f19e01c8d9cd97f171eaf6a5d469129e9e97af
parent a422e6afe37279c7d99291ae910e3c39f95d715b
Author: Jack Mordaunt <jackmordaunt@gmail.com>
Date:   Thu,  6 May 2021 17:18:06 +0800

feat(DecodeAll): export func that returns all decoded images

Diffstat:
M
reader.go
 | 
67
+++++++++++++++++++++++++++++++++++++++++++------------------------

1 file changed, 43 insertions(+), 24 deletions(-)
diff --git a/reader.go b/reader.go
@@ -7,8 +7,6 @@ import (
 	"image"
 	"io"
 	"io/ioutil"
-
-	"github.com/pkg/errors"
 )
 
 var jpeg2000header = []byte{0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20}
@@ -17,44 +15,75 @@ var jpeg2000header = []byte{0x00, 0x00, 0x00, 0x0c, 0x6a, 0x50, 0x20, 0x20}
 // ignoring all other sizes. The format returned will be whatever the icon data
 // is, typically jpeg or png.
 func Decode(r io.Reader) (image.Image, error) {
+	icons, err := decode(r)
+	if err != nil {
+		return nil, err
+	}
+	var biggest iconReader
+	for _, icon := range icons {
+		if icon.Size > biggest.Size {
+			biggest = icon
+		}
+	}
+	img, _, err := image.Decode(biggest.r)
+	if err != nil {
+		return nil, fmt.Errorf("decoding largest image: %w", err)
+	}
+	return img, nil
+}
+
+// DecodeAll extracts all icon resolutions present in the icns data.
+func DecodeAll(r io.Reader) (images []image.Image, err error) {
+	icons, err := decode(r)
+	if err != nil {
+		return nil, err
+	}
+	for _, icon := range icons {
+		img, _, err := image.Decode(icon.r)
+		if err != nil {
+			return nil, fmt.Errorf("decoding %q icon: %w", icon.OsType, err)
+		}
+		images = append(images, img)
+	}
+	return images, nil
+}
+
+func decode(r io.Reader) (icons []iconReader, err error) {
 	data, err := ioutil.ReadAll(r)
 	if err != nil {
 		return nil, err
 	}
-	icnsHeader := data[0:4]
-	if string(icnsHeader) != "icns" {
+	var (
+		header   = data[0:4]
+		fileSize = binary.BigEndian.Uint32(data[4:8])
+		read     = uint32(8)
+	)
+	if string(header) != "icns" {
 		return nil, fmt.Errorf("invalid header for icns file")
 	}
-	fileSize := binary.BigEndian.Uint32(data[4:8])
-	icons := []iconReader{}
-	read := uint32(8)
 	for read < fileSize {
 		next := data[read : read+4]
 		read += 4
 		switch string(next) {
 		case "TOC ":
 			tocSize := binary.BigEndian.Uint32(data[read : read+4])
-			read += tocSize-4 // size includes header and size fields
+			read += tocSize - 4 // size includes header and size fields
 			continue
 		case "icnV":
 			read += 4
 			continue
 		}
-
 		dataSize := binary.BigEndian.Uint32(data[read : read+4])
 		read += 4
 		if dataSize == 0 {
 			continue // no content, we're not interested
 		}
-
 		iconData := data[read : read+dataSize-8]
-		read += dataSize-8 // size includes header and size fields
-
+		read += dataSize - 8 // size includes header and size fields
 		if isOsType(string(next)) {
 			if bytes.Equal(iconData[:8], jpeg2000header) {
 				continue // skipping JPEG2000
 			}
-
 			icons = append(icons, iconReader{
 				OsType: osTypeFromID(string(next)),
 				r:      bytes.NewBuffer(iconData),
@@ -64,17 +93,7 @@ func Decode(r io.Reader) (image.Image, error) {
 	if len(icons) == 0 {
 		return nil, fmt.Errorf("no icons found")
 	}
-	var biggest iconReader
-	for _, icon := range icons {
-		if icon.Size > biggest.Size {
-			biggest = icon
-		}
-	}
-	img, _, err := image.Decode(biggest.r)
-	if err != nil {
-		return nil, errors.Wrap(err, "decoding largest image")
-	}
-	return img, nil
+	return icons, nil
 }
 
 type iconReader struct {