icns

commit 53997348b8910014cc39e77d121af9f7e8e381f3
parent e6262f6023aba2df14b9f86976dcf57364f33acc
Author: Jack Mordaunt <jackmordaunt@gmail.com>
Date:   Sat, 17 Feb 2018 23:48:53 +0100

[+] Introduced Decoder func with unit test.

Diffstat:
M
icns_test.go
 | 
58
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
reader.go
 | 
70
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 128 insertions(+), 0 deletions(-)
diff --git a/icns_test.go b/icns_test.go
@@ -13,6 +13,64 @@ import (
 	"github.com/pkg/errors"
 )
 
+// TestDecode relies on Encode being correct.
+func TestDecode(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		desc string
+		img  image.Image
+
+		wantErr bool
+	}{
+		{
+			"valid rectangle icon",
+			rect(0, 0, 1024, 1024),
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.desc, func(st *testing.T) {
+			buf := bytes.NewBuffer(nil)
+			if err := Encode(buf, tt.img); err != nil {
+				st.Fatalf("unexpected error while encoding: %v", err)
+			}
+			img, err := Decode(buf)
+			if !tt.wantErr && err != nil {
+				st.Fatalf("unexpected error: %v", err)
+			}
+			if tt.wantErr && err == nil {
+				st.Fatalf("wanted error, got nil")
+			}
+			if !imageCompare(img, tt.img) {
+				st.Fatalf("decoded image is incorrect")
+			}
+		})
+	}
+}
+
+func imageCompare(left, right image.Image) bool {
+	if left == nil && right == nil {
+		return true
+	}
+	if left == nil && right != nil {
+		return false
+	}
+	if left != nil && right == nil {
+		return false
+	}
+	lb := left.Bounds()
+	for ii := lb.Min.X; ii <= lb.Max.X; ii++ {
+		for kk := lb.Min.Y; kk <= lb.Max.Y; kk++ {
+			lr, lg, lb, la := left.At(ii, kk).RGBA()
+			rr, rg, rb, ra := right.At(ii, kk).RGBA()
+			if lr != rr || lg != rg || lb != rb || la != ra {
+				return false
+			}
+		}
+	}
+	return true
+}
+
 // TestEncode tests for input validation, sanity checks and errors.
 // The validity of the encoding is not tested here.
 // Super large images are not tested because the resizing takes too
diff --git a/reader.go b/reader.go
@@ -0,0 +1,70 @@
+package icns
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"image"
+	"io"
+	"io/ioutil"
+)
+
+// Decode finds the largest icon listed in the icns file and returns it,
+// 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) {
+	data, err := ioutil.ReadAll(r)
+	if err != nil {
+		return nil, err
+	}
+	icnsHeader := data[0:4]
+	if string(icnsHeader) != "icns" {
+		return nil, errors.New("invalid header for icns file")
+	}
+	fileSize := binary.BigEndian.Uint32(data[4:8])
+	icons := []OsType{}
+	datalist := []io.Reader{}
+	read := uint32(8)
+	for read < fileSize {
+		next := data[read : read+4]
+		read += 4
+		switch string(next) {
+		case "TOC ":
+			read += 4
+			continue
+		case "icnV":
+			read += 4
+			continue
+		}
+		if isOsType(string(next)) {
+			iconSize := binary.BigEndian.Uint32(data[read : read+4])
+			read += 4
+			iconData := data[read : read+iconSize]
+			read += iconSize
+			icons = append(icons, osTypeFromID(string(next)))
+			datalist = append(datalist, bytes.NewBuffer(iconData))
+		}
+	}
+	var max OsType
+	var maxData io.Reader
+	for ii, i := range icons {
+		if i.Size > max.Size {
+			max = i
+			maxData = datalist[ii]
+		}
+	}
+	img, _, err := image.Decode(maxData)
+	if err != nil {
+		return nil, err
+	}
+	return img, nil
+}
+
+func isOsType(ID string) bool {
+	_, ok := getTypeFromID(ID)
+	return ok
+}
+
+func init() {
+	image.RegisterFormat("icns", "icns", Decode, nil)
+}