examples: add imageviewer

1 files changed, 104 insertions, 0 deletions

diff --git a/examples/imageviewer/util.go b/examples/imageviewer/util.go
new file mode 100644
index 0000000..94f25fb
--- /dev/null
+++ b/examples/imageviewer/util.go
@@ -0,0 +1,104 @@
+package main
+
+import (
+	"image"
+	"image/color"
+	"image/draw"
+	"sync"
+
+	"github.com/golang/freetype/truetype"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+type concurrentFace struct {
+	mu   sync.Mutex
+	face font.Face
+}
+
+func (cf *concurrentFace) Close() error {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Close()
+}
+
+func (cf *concurrentFace) Glyph(dot fixed.Point26_6, r rune) (dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Glyph(dot, r)
+}
+
+func (cf *concurrentFace) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphBounds(r)
+}
+
+func (cf *concurrentFace) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphAdvance(r)
+}
+
+func (cf *concurrentFace) Kern(r0, r1 rune) fixed.Int26_6 {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Kern(r0, r1)
+}
+
+func (cf *concurrentFace) Metrics() font.Metrics {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Metrics()
+}
+
+func TTFToFace(ttf []byte, size float64) (font.Face, error) {
+	font, err := truetype.Parse(ttf)
+	if err != nil {
+		return nil, err
+	}
+	return &concurrentFace{face: truetype.NewFace(font, &truetype.Options{
+		Size: size,
+	})}, nil
+}
+
+func DrawText(text string, face font.Face, clr color.Color) image.Image {
+	drawer := &font.Drawer{
+		Src:  &image.Uniform{clr},
+		Face: face,
+		Dot:  fixed.P(0, 0),
+	}
+	b26_6, _ := drawer.BoundString(text)
+	bounds := image.Rect(
+		b26_6.Min.X.Floor(),
+		b26_6.Min.Y.Floor(),
+		b26_6.Max.X.Ceil(),
+		b26_6.Max.Y.Ceil(),
+	)
+	drawer.Dst = image.NewRGBA(bounds)
+	drawer.DrawString(text)
+	return drawer.Dst
+}
+
+func DrawCentered(dst draw.Image, r image.Rectangle, src image.Image, op draw.Op) {
+	if src == nil {
+		return
+	}
+	bounds := src.Bounds()
+	center := bounds.Min.Add(bounds.Max).Div(2)
+	target := r.Min.Add(r.Max).Div(2)
+	delta := target.Sub(center)
+	draw.Draw(dst, bounds.Add(delta).Intersect(r), src, bounds.Min, op)
+}
+
+func DrawLeftCentered(dst draw.Image, r image.Rectangle, src image.Image, op draw.Op) {
+	if src == nil {
+		return
+	}
+	bounds := src.Bounds()
+	leftCenter := image.Pt(bounds.Min.X, (bounds.Min.Y+bounds.Max.Y)/2)
+	target := image.Pt(r.Min.X, (r.Min.Y+r.Max.Y)/2)
+	delta := target.Sub(leftCenter)
+	draw.Draw(dst, bounds.Add(delta).Intersect(r), src, bounds.Min, op)
+}