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add method to change drawing interpolator

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default interpolator used for drawing text and images is draw.BiLinear
and it's rather slow against e.g. draw.NearestNeighbor
The difference is significant especially on weak hardware
e.g. on raspberry pi zero (ARMv6) drawing short string can be 10-16 times
faster with draw.NearestNeighbor

Signed-off-by: George Stark <stark.georgy@gmail.com>
This commit is contained in:
George Stark 2021-03-30 13:30:23 +03:00
parent af4cd58078
commit 2084297999
1 changed files with 8 additions and 2 deletions
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10
context.go
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@ -77,6 +77,7 @@ type Context struct {
fontHeight float64
matrix Matrix
stack []*Context
interpolator draw.Interpolator
}
// NewContext creates a new image.RGBA with the specified width and height
@ -109,9 +110,14 @@ func NewContextForRGBA(im *image.RGBA) *Context {
fontFace: basicfont.Face7x13,
fontHeight: 13,
matrix: Identity(),
interpolator: draw.BiLinear,
}
}
func (dc *Context) SetInterpolator(interpolator draw.Interpolator) {
dc.interpolator = interpolator
}
// GetCurrentPoint will return the current point and if there is a current point.
// The point will have been transformed by the context's transformation matrix.
func (dc *Context) GetCurrentPoint() (Point, bool) {
@ -673,7 +679,7 @@ func (dc *Context) DrawImageAnchored(im image.Image, x, y int, ax, ay float64) {
s := im.Bounds().Size()
x -= int(ax * float64(s.X))
y -= int(ay * float64(s.Y))
transformer := draw.BiLinear
transformer := dc.interpolator
fx, fy := float64(x), float64(y)
m := dc.matrix.Translate(fx, fy)
s2d := f64.Aff3{m.XX, m.XY, m.X0, m.YX, m.YY, m.Y0}
@ -728,7 +734,7 @@ func (dc *Context) drawString(im *image.RGBA, s string, x, y float64) {
continue
}
sr := dr.Sub(dr.Min)
transformer := draw.BiLinear
transformer := dc.interpolator
fx, fy := float64(dr.Min.X), float64(dr.Min.Y)
m := dc.matrix.Translate(fx, fy)
s2d := f64.Aff3{m.XX, m.XY, m.X0, m.YX, m.YY, m.Y0}