icns

commit 816e624c745694df4f3f7aa74b78b7211e394d84
parent 38c96fa1f43944821a92515e958111ca72d1df56
Author: Jack Mordaunt <jackmordaunt.dev@gmail.com>
Date:   Wed, 16 Sep 2026 21:30:03 -0400

icns: measure images by their dimensions, not their bounds

An image whose bounds do not start at the origin, such as a SubImage,
reported its far corner as its size. That selected too large an icon tier and
upscaled the source, and the too-small error printed the wrong dimensions.

Diffstat:
M
error.go
 | 
4
++--
M
icns.go
 | 
10
+++-------

2 files changed, 5 insertions(+), 9 deletions(-)
diff --git a/error.go b/error.go
@@ -29,7 +29,7 @@ type ErrImageTooSmall struct {
 }
 
 func (err ErrImageTooSmall) Error() string {
-	b := err.image.Bounds().Max
+	b := err.image.Bounds()
 	format := "image is too small: %dx%d, need at least %dx%d"
-	return fmt.Sprintf(format, b.X, b.Y, err.need, err.need)
+	return fmt.Sprintf(format, b.Dx(), b.Dy(), err.need, err.need)
 }
diff --git a/icns.go b/icns.go
@@ -123,15 +123,11 @@ func findNearestSize(img image.Image) uint {
 	return 0
 }
 
+// biggestSide returns the larger dimension of img. Bounds need not start at
+// the origin, so measure the rectangle rather than its far corner.
 func biggestSide(img image.Image) uint {
-	var size uint
 	b := img.Bounds()
-	w, h := uint(b.Max.X), uint(b.Max.Y)
-	size = w
-	if h > size {
-		size = h
-	}
-	return size
+	return uint(max(b.Dx(), b.Dy(), 0))
 }
 
 // sizesFrom returns a slice containing the sizes less than and including max.