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go-opengl-pixel
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add Canvas.SetComposeMethod

This commit is contained in:
faiface 2017-04-10 00:30:50 +02:00
parent 58e8b8f892
commit 3d3f1c6e11
1 changed files with 36 additions and 1 deletions
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37
pixelgl/canvas.go
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@ -19,11 +19,14 @@ type Canvas struct {
gf *GLFrame
shader *glhf.Shader
cmp pixel.ComposeMethod
mat mgl32.Mat3
col mgl32.Vec4
smooth bool
}
var _ pixel.ComposeTarget = (*Canvas)(nil)
// NewCanvas creates a new empty, fully transparent Canvas with given bounds. If the smooth flag is
// set, then stretched Pictures will be smoothed and will not be drawn pixely onto this Canvas.
func NewCanvas(bounds pixel.Rect, smooth bool) *Canvas {
@ -107,6 +110,12 @@ func (c *Canvas) SetColorMask(col color.Color) {
}
}
// SetComposeMethod sets a Porter-Duff composition method to be used in the following draws onto
// this Canvas.
func (c *Canvas) SetComposeMethod(cmp pixel.ComposeMethod) {
c.cmp = cmp
}
// SetBounds resizes the Canvas to the new bounds. Old content will be preserved.
func (c *Canvas) SetBounds(bounds pixel.Rect) {
c.gf.SetBounds(bounds)
@ -135,6 +144,32 @@ func (c *Canvas) setGlhfBounds() {
glhf.Bounds(bx, by, bw, bh)
}
// must be manually called inside mainthread
func (c *Canvas) setBlendFunc() {
switch c.cmp {
case pixel.ComposeOver:
glhf.BlendFunc(glhf.One, glhf.OneMinusSrcAlpha)
case pixel.ComposeIn:
glhf.BlendFunc(glhf.DstAlpha, glhf.Zero)
case pixel.ComposeOut:
glhf.BlendFunc(glhf.OneMinusDstAlpha, glhf.Zero)
case pixel.ComposeAtop:
glhf.BlendFunc(glhf.DstAlpha, glhf.OneMinusSrcAlpha)
case pixel.ComposeDstOver:
glhf.BlendFunc(glhf.OneMinusDstAlpha, glhf.One)
case pixel.ComposeDstIn:
glhf.BlendFunc(glhf.Zero, glhf.SrcAlpha)
case pixel.ComposeDstOut:
glhf.BlendFunc(glhf.Zero, glhf.OneMinusSrcAlpha)
case pixel.ComposeDstAtop:
glhf.BlendFunc(glhf.OneMinusDstAlpha, glhf.SrcAlpha)
case pixel.ComposeXor:
glhf.BlendFunc(glhf.OneMinusDstAlpha, glhf.OneMinusSrcAlpha)
default:
panic(errors.New("Canvas: invalid compose method"))
}
}
// Clear fills the whole Canvas with a single color.
func (c *Canvas) Clear(color color.Color) {
c.gf.Dirty()
@ -188,7 +223,7 @@ func (ct *canvasTriangles) draw(tex *glhf.Texture, bounds pixel.Rect) {
mainthread.CallNonBlock(func() {
ct.dst.setGlhfBounds()
glhf.BlendFunc(glhf.One, glhf.OneMinusSrcAlpha)
ct.dst.setBlendFunc()
frame := ct.dst.gf.Frame()
shader := ct.dst.shader