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