icns

commit ce05490eaa42c1a34c59ebb2d36c77eb8b189460
parent 4d4e3548ef07398447e3b237a26960a8ab379938
Author: Jack Mordaunt <jackmordaunt@gmail.com>
Date:   Fri,  9 Feb 2018 13:51:16 +0100

[*] Misc fixes.

Image size guard to reject small images.
Fixed bug in `findNearestSize`.
Annotated panic in `getType` with the image size.

Diffstat:
A
error.go
 | 
22
++++++++++++++++++++++
M
icns.go
 | 
7
+++++--

2 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/error.go b/error.go
@@ -0,0 +1,22 @@
+package icns
+
+import (
+	"fmt"
+	"image"
+)
+
+// ErrImageTooSmall is returned when the image is too small to process.
+type ErrImageTooSmall struct {
+	need  int
+	image image.Image
+}
+
+func (err ErrImageTooSmall) Error() string {
+	b := err.image.Bounds().Max
+	format := "image is too small: %dx%d, need at least %dx%d"
+	return fmt.Sprintf(format, b.X, b.Y, err.need, err.need)
+}
+
+func panicf(format string, values ...interface{}) {
+	panic(fmt.Sprintf(format, values...))
+}
diff --git a/icns.go b/icns.go
@@ -27,6 +27,9 @@ func Encode(wr io.Writer, img image.Image) error {
 // preserving the aspect ratio.
 func NewIconSet(img image.Image, interp InterpolationFunction) (*IconSet, error) {
 	biggest := findNearestSize(img)
+	if biggest == 0 {
+		return nil, ErrImageTooSmall{image: img, need: 16}
+	}
 	icons := []*Icon{}
 	for _, size := range sizesFrom(biggest) {
 		iconImg := resize.Resize(size, size, img, interp)
@@ -63,7 +66,7 @@ var sizes = []uint{
 func findNearestSize(img image.Image) uint {
 	size := biggestSide(img)
 	for _, s := range sizes {
-		if size > s {
+		if size >= s {
 			return s
 		}
 	}
@@ -105,7 +108,7 @@ var types = map[uint]OsType{
 func getType(size uint) OsType {
 	v, ok := types[size]
 	if !ok {
-		panic("could not select the correct icon type")
+		panicf("could not select the correct icon type for size %d", size)
 	}
 	return v
 }