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hochwasser/pixelflut/canvas.go

97 lines
2.0 KiB
Go

package pixelflut
import (
"bufio"
"encoding/hex"
"image"
"image/color"
"log"
"net"
)
// CanvasSize returns the size of the canvas as returned by the server
func CanvasSize(address string) (int, int) {
conn, err := net.Dial("tcp", address)
if err != nil {
log.Fatal(err)
}
defer conn.Close()
conn.Write([]byte("SIZE\n"))
reader := bufio.NewReader(conn)
res, err := reader.ReadSlice('\n')
if err != nil {
log.Fatal(err)
}
return parseXY(res[5:])
}
// FetchImage asynchronously uses `conns` to fetch pixels within `bounds` from
// a pixelflut server at `address`, and writes them into the returned Image.
// If bounds is nil, the server's entire canvas is fetched.
func FetchImage(bounds *image.Rectangle, address string, conns int, stop chan bool) (img *image.NRGBA) {
if bounds == nil {
x, y := CanvasSize(address)
bounds = &image.Rectangle{Max: image.Pt(x, y)}
}
img = image.NewNRGBA(*bounds)
cmds := cmdsFetchImage(*bounds).Chunk(conns)
for i := 0; i < conns; i++ {
conn, err := net.Dial("tcp", address)
if err != nil {
log.Fatal(err)
}
go readPixels(img, conn, stop)
go bombConn(cmds[i], 0, 0, conn, stop)
}
return img
}
func readPixels(target *image.NRGBA, conn net.Conn, stop chan bool) {
reader := bufio.NewReader(conn)
col := make([]byte, 4)
for {
select {
case <-stop:
return
default:
res, err := reader.ReadSlice('\n')
if err != nil {
log.Fatal(err)
}
// parse response ("PX <x> <y> <rrggbb>")
colorStart := len(res) - 7
x, y := parseXY(res[3:colorStart])
hex.Decode(col, res[colorStart:len(res)-1])
target.SetNRGBA(x, y, color.NRGBA{col[0], col[1], col[2], col[3]})
}
}
}
func parseXY(xy []byte) (int, int) {
last := len(xy) - 1
yStart := last - 1 // y is at least one char long
for ; yStart >= 0; yStart-- {
if xy[yStart] == ' ' {
break
}
}
x := asciiToInt(xy[:yStart])
y := asciiToInt(xy[yStart+1 : last])
return x, y
}
func asciiToInt(buf []byte) (v int) {
for _, c := range buf {
v = v*10 + int(c-'0')
}
return v
}