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// Copyright 2014 The Go 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 portable implements a sprite Engine using the image package.
//
// It is intended to serve as a reference implementation for testing
// other sprite Engines written against OpenGL, or other more exotic
// modern hardware interfaces.
package portable // import "golang.org/x/mobile/exp/sprite/portable"
import (
"image"
"image/draw"
xdraw "golang.org/x/image/draw"
"golang.org/x/image/math/f64"
"golang.org/x/mobile/event/size"
"golang.org/x/mobile/exp/f32"
"golang.org/x/mobile/exp/sprite"
"golang.org/x/mobile/exp/sprite/clock"
)
// Engine builds a sprite Engine that renders onto dst.
func Engine(dst *image.RGBA) sprite.Engine {
return &engine{
dst: dst,
nodes: []*node{nil},
}
}
type node struct {
// TODO: move this into package sprite as Node.EngineFields.RelTransform??
relTransform f32.Affine
}
type texture struct {
m *image.RGBA
}
func (t *texture) Bounds() (w, h int) {
b := t.m.Bounds()
return b.Dx(), b.Dy()
}
func (t *texture) Download(r image.Rectangle, dst draw.Image) {
draw.Draw(dst, r, t.m, t.m.Bounds().Min, draw.Src)
}
func (t *texture) Upload(r image.Rectangle, src image.Image) {
draw.Draw(t.m, r, src, src.Bounds().Min, draw.Src)
}
func (t *texture) Release() {}
type engine struct {
dst *image.RGBA
nodes []*node
absTransforms []f32.Affine
}
func (e *engine) Register(n *sprite.Node) {
if n.EngineFields.Index != 0 {
panic("portable: sprite.Node already registered")
}
o := &node{}
o.relTransform.Identity()
e.nodes = append(e.nodes, o)
n.EngineFields.Index = int32(len(e.nodes) - 1)
}
func (e *engine) Unregister(n *sprite.Node) {
panic("todo")
}
func (e *engine) LoadTexture(m image.Image) (sprite.Texture, error) {
b := m.Bounds()
w, h := b.Dx(), b.Dy()
t := &texture{m: image.NewRGBA(image.Rect(0, 0, w, h))}
t.Upload(b, m)
return t, nil
}
func (e *engine) SetSubTex(n *sprite.Node, x sprite.SubTex) {
n.EngineFields.Dirty = true // TODO: do we need to propagate dirtiness up/down the tree?
n.EngineFields.SubTex = x
}
func (e *engine) SetTransform(n *sprite.Node, m f32.Affine) {
n.EngineFields.Dirty = true // TODO: do we need to propagate dirtiness up/down the tree?
e.nodes[n.EngineFields.Index].relTransform = m
}
func (e *engine) Render(scene *sprite.Node, t clock.Time, sz size.Event) {
// Affine transforms are done in geom.Pt. When finally drawing
// the geom.Pt onto an image.Image we need to convert to system
// pixels. We scale by sz.PixelsPerPt to do this.
e.absTransforms = append(e.absTransforms[:0], f32.Affine{
{sz.PixelsPerPt, 0, 0},
{0, sz.PixelsPerPt, 0},
})
e.render(scene, t)
}
func (e *engine) render(n *sprite.Node, t clock.Time) {
if n.EngineFields.Index == 0 {
panic("portable: sprite.Node not registered")
}
if n.Arranger != nil {
n.Arranger.Arrange(e, n, t)
}
// Push absTransforms.
// TODO: cache absolute transforms and use EngineFields.Dirty?
rel := &e.nodes[n.EngineFields.Index].relTransform
m := f32.Affine{}
m.Mul(&e.absTransforms[len(e.absTransforms)-1], rel)
e.absTransforms = append(e.absTransforms, m)
if x := n.EngineFields.SubTex; x.T != nil {
// Affine transforms work in geom.Pt, which is entirely
// independent of the number of pixels in a texture. A texture
// of any image.Rectangle bounds rendered with
//
// Affine{{1, 0, 0}, {0, 1, 0}}
//
// should have the dimensions (1pt, 1pt). To do this we divide
// by the pixel width and height, reducing the texture to
// (1px, 1px) of the destination image. Multiplying by
// sz.PixelsPerPt, done in Render above, makes it (1pt, 1pt).
dx, dy := x.R.Dx(), x.R.Dy()
if dx > 0 && dy > 0 {
m.Scale(&m, 1/float32(dx), 1/float32(dy))
// TODO(nigeltao): delete the double-inverse: one here and one
// inside func affine.
m.Inverse(&m) // See the documentation on the affine function.
affine(e.dst, x.T.(*texture).m, x.R, nil, &m, draw.Over)
}
}
for c := n.FirstChild; c != nil; c = c.NextSibling {
e.render(c, t)
}
// Pop absTransforms.
e.absTransforms = e.absTransforms[:len(e.absTransforms)-1]
}
func (e *engine) Release() {}
// affine draws each pixel of dst using bilinear interpolation of the
// affine-transformed position in src. This is equivalent to:
//
// for each (x,y) in dst:
// dst(x,y) = bilinear interpolation of src(a*(x,y))
//
// While this is the simpler implementation, it can be counter-
// intuitive as an affine transformation is usually described in terms
// of the source, not the destination. For example, a scale transform
//
// Affine{{2, 0, 0}, {0, 2, 0}}
//
// will produce a dst that is half the size of src. To perform a
// traditional affine transform, use the inverse of the affine matrix.
func affine(dst *image.RGBA, src image.Image, srcb image.Rectangle, mask image.Image, a *f32.Affine, op draw.Op) {
// For legacy compatibility reasons, the matrix a transforms from dst-space
// to src-space. The golang.org/x/image/draw package's matrices transform
// from src-space to dst-space, so we invert (and adjust for different
// origins).
i := *a
i[0][2] += float32(srcb.Min.X)
i[1][2] += float32(srcb.Min.Y)
i.Inverse(&i)
i[0][2] += float32(dst.Rect.Min.X)
i[1][2] += float32(dst.Rect.Min.Y)
m := f64.Aff3{
float64(i[0][0]),
float64(i[0][1]),
float64(i[0][2]),
float64(i[1][0]),
float64(i[1][1]),
float64(i[1][2]),
}
// TODO(nigeltao): is the caller or callee responsible for detecting
// transforms that are simple copies or scales, for which there are faster
// implementations in the xdraw package.
xdraw.ApproxBiLinear.Transform(dst, m, src, srcb, xdraw.Op(op), &xdraw.Options{
SrcMask: mask,
})
}