Improve icon rendering: fix scaling and centering for emoji, FontAwesome, and SVG icons

cbdt.go

@@ -175,9 +175,12 @@ func renderCBDTGlyph(r rune, targetSize int, scale float64) (image.Image, bool)
 	raw := emojiCBDT.imgs[idx]
 
 	displaySize := int(float64(targetSize) * scale)
-	if displaySize < 1 {
+	if displaySize > targetSize {
 		displaySize = targetSize
 	}
+	if displaySize < 1 {
+		displaySize = 1
+	}
 
 	scaled := raw
 	if raw.Bounds().Dx() != displaySize || raw.Bounds().Dy() != displaySize {

fontawesome.go

@@ -115,11 +115,14 @@ func renderFAGlyph(style faStyle, name string, size int, scale float64) (image.I
 
 	rgba := image.NewRGBA(image.Rect(0, 0, size, size))
 
-	offX := (size - int(fontSize)) / 2
+	adv := font.MeasureString(face, string(cp)).Ceil()
+	offX := (size - adv) / 2
 	if offX < 0 {
-		offX = size / 8
+		offX = 0
 	}
-	baselineY := size * 7 / 10
+
+	metrics := face.Metrics()
+	baselineY := (size + metrics.Ascent.Ceil() - metrics.Descent.Ceil()) / 2
 
 	d := font.Drawer{
 		Dst:  rgba,

icons.go

@@ -153,12 +153,12 @@ func svgToPNG(svgPath string, targetSize int, scale float64) (image.Image, error
 		scale = 0.55
 	}
 
-	renderSize := targetSize
-	if scale < 1 {
-		renderSize = int(float64(targetSize) * scale)
-		if renderSize < 1 {
-			renderSize = 1
-		}
+	renderSize := int(float64(targetSize) * scale)
+	if renderSize > targetSize {
+		renderSize = targetSize
+	}
+	if renderSize < 1 {
+		renderSize = 1
 	}
 
 	cmd := exec.Command("rsvg-convert",