Bring over X canvas package

x/canvas/texture.go

@@ -0,0 +1,106 @@
+package xcanvas
+
+import "image"
+import "image/color"
+import "github.com/jezek/xgbutil/xgraphics"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+// Texture is a read-only image texture that can be quickly written to a canvas.
+// It must be closed manually after use.
+type Texture struct {
+	pix         []uint8
+	stride      int
+	rect        image.Rectangle
+	transparent bool
+}
+
+// NewTextureFrom creates a new texture from a source image.
+func NewTextureFrom (source image.Image) *Texture {
+	bounds := source.Bounds()
+	texture := &Texture {
+		pix:    make([]uint8, bounds.Dx() * bounds.Dy() * 4),
+		stride: bounds.Dx() * 4,
+		rect:   bounds.Sub(bounds.Min),
+	}
+
+	index := 0
+	var point image.Point
+	for point.Y = bounds.Min.Y; point.Y < bounds.Max.Y; point.Y ++ {
+	for point.X = bounds.Min.X; point.X < bounds.Max.X; point.X ++ {
+		r, g, b, a := source.At(point.X, point.Y).RGBA()
+		texture.pix[index + 0] = uint8(b >> 8)
+		texture.pix[index + 1] = uint8(g >> 8)
+		texture.pix[index + 2] = uint8(r >> 8)
+		texture.pix[index + 3] = uint8(a >> 8)
+		index += 4
+
+		if a != 0xFFFF {
+			texture.transparent = true
+		}
+	}}
+
+	return texture
+}
+
+func (this *Texture) BGRAAt (x, y int) xgraphics.BGRA {
+	if !(image.Point{ x, y }.In(this.rect)) {
+		return xgraphics.BGRA { }
+	}
+	index := this.PixOffset(x, y)
+	return xgraphics.BGRA {
+		B: this.pix[index    ],
+		G: this.pix[index + 1],
+		R: this.pix[index + 2],
+		A: this.pix[index + 3],
+	}
+}
+
+func (this *Texture) At (x, y int) color.Color {
+	return this.BGRAAt(x, y)
+}
+
+// Bounds returns the bounding rectangle of this texture.
+func (this *Texture) Bounds () image.Rectangle {
+	return this.rect
+}
+
+func (this *Texture) ColorModel () color.Model {
+	return xgraphics.BGRAModel
+}
+
+// Opaque reports whether or not the texture is fully opaque.
+func (this *Texture) Opaque () bool {
+	return !this.transparent
+}
+
+func (this *Texture) PixOffset (x, y int) int {
+	x = wrap(x, this.rect.Min.X, this.rect.Max.X)
+	y = wrap(y, this.rect.Min.Y, this.rect.Max.Y)
+	return x * 4 + y * this.stride
+}
+
+// Close frees the texture from memory.
+func (this *Texture) Close () error {
+	// i lied we dont actually need to close this, but we will once this
+	// texture resides on the x server or in video memory.
+	return nil
+}
+
+// SubTexture returns a subset of this texture that points to the same data.
+func (this *Texture) SubTexture (bounds image.Rectangle) canvas.Texture {
+	clipped := *this
+	clipped.rect = bounds
+	return &clipped
+}
+
+// AssertTexture checks if a given canvas.Texture is a texture from this package.
+func AssertTexture (unknown canvas.Texture) *Texture {
+	if unknown == nil {
+		return nil
+	}
+	if tx, ok := unknown.(*Texture); ok {
+		return tx
+	} else {
+		panic("foregin texture implementation, i did not make this!")
+	}
+}