backend/x/canvas/plot.go

48 lines
1.4 KiB
Go

package xcanvas
import "image"
import "github.com/jezek/xgbutil/xgraphics"
type plottingContext struct {
image *xgraphics.Image
color xgraphics.BGRA
weight int
}
func (context plottingContext) square (center image.Point) (square image.Rectangle) {
return image.Rect(0, 0, context.weight, context.weight).
Sub(image.Pt(context.weight / 2, context.weight / 2)).
Add(center).
Intersect(context.image.Bounds())
}
func (context plottingContext) plot (center image.Point) {
square := context.square(center)
if context.color.A == 255 {
for y := square.Min.Y; y < square.Max.Y; y ++ {
for x := square.Min.X; x < square.Max.X; x ++ {
index := context.image.PixOffset(x, y)
context.image.Pix[index + 0] = context.color.B
context.image.Pix[index + 1] = context.color.G
context.image.Pix[index + 2] = context.color.R
context.image.Pix[index + 3] = context.color.A
}}
} else {
for y := square.Min.Y; y < square.Max.Y; y ++ {
for x := square.Min.X; x < square.Max.X; x ++ {
index := context.image.PixOffset(x, y)
pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
B: context.image.Pix[index + 0],
G: context.image.Pix[index + 1],
R: context.image.Pix[index + 2],
A: context.image.Pix[index + 3],
}, context.color)
context.image.Pix[index + 0] = pixel.B
context.image.Pix[index + 1] = pixel.G
context.image.Pix[index + 2] = pixel.R
context.image.Pix[index + 3] = pixel.A
}}
}
}