go.mobile/gl/glutil, go.mobile/app/debug: create glimage with pixel size

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://golang.org/cl/165940043

Author: crawshaw

app/debug/fps.go

@@ -11,6 +11,7 @@ import (
 	"image/draw"
 	"io/ioutil"
 	"log"
+	"math"
 	"runtime"
 	"sync"
 	"time"
@@ -57,7 +58,8 @@ func fpsInit() {
 	monofont.SetSrc(image.Black)
 	monofont.SetHinting(freetype.FullHinting)
 
-	fps.Image = glutil.NewImage(geom.Point{50, 12})
+	toPx := func(x geom.Pt) int { return int(math.Ceil(float64(geom.Pt(x).Px()))) }
+	fps.Image = glutil.NewImage(toPx(50), toPx(12))
 	monofont.SetDst(fps.Image.RGBA)
 	monofont.SetClip(fps.Bounds())
 	monofont.SetDPI(72 * float64(geom.PixelsPerPt))

gl/glutil/glimage.go

@@ -7,7 +7,6 @@ package glutil
 import (
 	"encoding/binary"
 	"image"
-	"math"
 	"sync"
 
 	"code.google.com/p/go.mobile/f32"
@@ -67,11 +66,9 @@ type Image struct {
 // NewImage creates an Image of the given size.
 //
 // Both a host-memory *image.RGBA and a GL texture are created.
-func NewImage(size geom.Point) *Image {
-	realx := int(math.Ceil(float64(size.X.Px())))
-	realy := int(math.Ceil(float64(size.Y.Px())))
-	dx := roundToPower2(realx)
-	dy := roundToPower2(realy)
+func NewImage(w, h int) *Image {
+	dx := roundToPower2(w)
+	dy := roundToPower2(h)
 
 	// TODO(crawshaw): Using VertexAttribPointer we can pass texture
 	// data with a stride, which would let us use the exact number of
@@ -81,7 +78,7 @@ func NewImage(size geom.Point) *Image {
 	glimage.Do(glInit)
 
 	img := &Image{
-		RGBA:      m.SubImage(image.Rect(0, 0, realx, realy)).(*image.RGBA),
+		RGBA:      m.SubImage(image.Rect(0, 0, w, h)).(*image.RGBA),
 		Texture:   gl.GenTexture(),
 		texWidth:  dx,
 		texHeight: dy,

gl/glutil/glimage_test.go

@@ -67,7 +67,7 @@ func TestImage(t *testing.T) {
 	gl.Clear(gl.COLOR_BUFFER_BIT)
 	gl.Viewport(0, 0, pixW, pixH)
 
-	m := NewImage(geom.Point{ptW, ptH})
+	m := NewImage(src.Bounds().Dx(), src.Bounds().Dy())
 	b := m.RGBA.Bounds()
 	draw.Draw(m.RGBA, b, src, src.Bounds().Min, draw.Src)
 	m.Upload()