ev3dev/fb: add support for XRGB

fb/xrgb.go

@@ -0,0 +1,109 @@
+// Copyright ©2016 The ev3go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fb
+
+import (
+	"errors"
+	"image"
+	"image/color"
+	"image/draw"
+)
+
+// NewXRGB returns a new XRGB image with the given bounds.
+func NewXRGB(r image.Rectangle) *XRGB {
+	w, h := r.Dx(), r.Dy()
+	stride := 4 * w
+	pix := make([]uint8, stride*h)
+	return &XRGB{Pix: pix, Stride: stride, Rect: r}
+}
+
+// NewXRGBWith returns a new XRGB image with the given bounds,
+// backed by the []byte, pix. If stride is zero, a working stride
+// is computed. If the length of pix is less than stride*h, an
+// error is returned.
+func NewXRGBWith(pix []byte, r image.Rectangle, stride int) (draw.Image, error) {
+	w, h := r.Dx(), r.Dy()
+	if stride == 0 {
+		stride = 4 * w
+	}
+	if len(pix) < stride*h {
+		return nil, errors.New("ev3dev: bad pixel buffer length")
+	}
+	return &XRGB{Pix: pix, Stride: stride, Rect: r}, nil
+}
+
+// XRGB is an in-memory image whose At method returns PixelXRGB values.
+type XRGB struct {
+	// Pix holds the image's pixels, as 32 bit XRGB
+	// values stored in little-endian order.
+	// The pixel at (x, y) is the four bytes at
+	// Pix[4*(x-Rect.Min.X) + (y-Rect.Min.Y)*Stride].
+	Pix []uint8
+	// Stride is the Pix stride (in bytes) between
+	// vertically adjacent pixels.
+	Stride int
+	// Rect is the image's bounds.
+	Rect image.Rectangle
+}
+
+// ColorModel returns the XRGB color model.
+func (p *XRGB) ColorModel() color.Model { return RGB565Model }
+
+// Bounds returns the bounding rectangle for the image.
+func (p *XRGB) Bounds() image.Rectangle { return p.Rect }
+
+// At returns the color of the pixel at (x, y).
+func (p *XRGB) At(x, y int) color.Color {
+	if !(image.Point{x, y}.In(p.Rect)) {
+		return color.RGBA{}
+	}
+	i := p.pixOffset(x, y)
+	return PixelXRGB{R: p.Pix[i+2], G: p.Pix[i+1], B: p.Pix[i]}
+}
+
+// Set sets the color of the pixel at (x, y) to c.
+func (p *XRGB) Set(x, y int, c color.Color) {
+	if !(image.Point{x, y}.In(p.Rect)) {
+		return
+	}
+	i := p.pixOffset(x, y)
+	xrgb := XRGBModel.Convert(c).(PixelXRGB)
+	p.Pix[i+2] = xrgb.R
+	p.Pix[i+1] = xrgb.G
+	p.Pix[i] = xrgb.B
+}
+
+// pixOffset returns the index into p.Pix for the first byte
+// containing the pixel at (x, y).
+func (p *XRGB) pixOffset(x, y int) int {
+	return 4*(x-p.Rect.Min.X) + (y-p.Rect.Min.Y)*p.Stride
+}
+
+// PixelXRGB is an XRGB pixel.
+type PixelXRGB struct {
+	R, G, B byte
+}
+
+// RGBA returns the RGBA values for the receiver.
+func (c PixelXRGB) RGBA() (r, g, b, a uint32) {
+	r = uint32(c.R)
+	r |= r << 8
+	g = uint32(c.G)
+	g |= g << 8
+	b = uint32(c.B)
+	b |= b << 8
+	return r, g, b, 0xffff
+}
+
+// XRGBModel is the color model for XRGB images.
+var XRGBModel color.Model = color.ModelFunc(xrgbModel)
+
+func xrgbModel(c color.Color) color.Color {
+	if _, ok := c.(PixelXRGB); ok {
+		return c
+	}
+	r, g, b, _ := c.RGBA()
+	return PixelXRGB{R: uint8(r >> 8), G: uint8(g >> 8), B: uint8(b >> 8)}
+}

fb/xrgb_test.go

@@ -0,0 +1,52 @@
+// Copyright ©2016 The ev3go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fb
+
+import (
+	"image/draw"
+	"image/png"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+func TestXRGB(t *testing.T) {
+	for _, test := range testImages {
+		golden := filepath.FromSlash("testdata/" + test + "-xrgb.png")
+
+		src, err := decodeImage(filepath.FromSlash("testdata/" + test + ".png"))
+		if err != nil {
+			t.Fatalf("failed to read src image file %v.png: %v", test, err)
+		}
+
+		got := NewXRGB(src.Bounds())
+		draw.Draw(got, got.Bounds(), src, src.Bounds().Min, draw.Src)
+
+		if *genGolden {
+			f, err := os.Create(golden)
+			if err != nil {
+				t.Fatalf("failed to create golden image file %v-xrgb.png: %v", test, err)
+			}
+			defer f.Close()
+			err = png.Encode(f, got)
+			if err != nil {
+				t.Fatalf("failed to encode golden image %v-xrgb.png: %v", test, err)
+			}
+			continue
+		}
+
+		gol, err := decodeImage(golden)
+		if err != nil {
+			t.Fatalf("failed to read golden image file %v-xrgb.png: %v", test, err)
+		}
+		want := NewXRGB(gol.Bounds())
+		draw.Draw(want, want.Bounds(), gol, gol.Bounds().Min, draw.Src)
+
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("XRGB from source does not match expected image for %v test", test)
+		}
+	}
+}