137 lines
2.8 KiB
Go
137 lines
2.8 KiB
Go
// Copyright 2014, 2015 by Sascha L. Teichmann
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// Use of this source code is governed by the MIT license
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// that can be found in the LICENSE file.
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package common
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import (
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"bufio"
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"bytes"
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"errors"
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"image"
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"image/color"
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"image/draw"
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"image/png"
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"log"
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"os"
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"strconv"
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"sync"
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"time"
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"golang.org/x/crypto/blake2b"
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"github.com/bamiaux/rez"
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)
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// ResizeFilter is used to scale down the pyramid tiles.
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var ResizeFilter = rez.NewLanczosFilter(3)
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var rrand uint32
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var rrandmu sync.Mutex
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func reseed() uint32 {
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return uint32(time.Now().UnixNano() + int64(os.Getpid()))
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}
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func nextSuffix() string {
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rrandmu.Lock()
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r := rrand
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if r == 0 {
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r = reseed()
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}
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r = r*1664525 + 1013904223 // constants from Numerical Recipes
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rrand = r
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rrandmu.Unlock()
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return strconv.Itoa(int(1e9 + r%1e9))[1:]
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}
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func EncodeToMem(img image.Image) []byte {
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var buf bytes.Buffer
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enc := png.Encoder{CompressionLevel: png.BestCompression}
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if err := enc.Encode(&buf, img); err != nil {
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// This really should not happen.
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panic(err)
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}
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return buf.Bytes()
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}
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func SaveAsPNG(path string, img image.Image) (err error) {
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var file *os.File
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if file, err = os.Create(path); err != nil {
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return
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}
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writer := bufio.NewWriter(file)
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err = png.Encode(writer, img)
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writer.Flush()
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file.Close()
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return
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}
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func tmpName(tmpl string) (string, error) {
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tmpPre := tmpl + ".tmp"
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nconflict := 0
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for i := 0; i < 10000; i++ {
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tmp := tmpPre + nextSuffix()
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if _, err := os.Stat(tmp); err != nil {
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if os.IsNotExist(err) {
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return tmp, nil
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}
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return "", err
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}
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if nconflict++; nconflict > 10 {
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nconflict = 0
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rrand = reseed()
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}
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}
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return "", errors.New("cannot create temp name")
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}
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func SaveAsPNGAtomic(path string, img image.Image) (err error) {
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var tmpPath string
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if tmpPath, err = tmpName(path); err != nil {
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return
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}
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// Still a bit racy
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if err = SaveAsPNG(tmpPath, img); err != nil {
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return
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}
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return os.Rename(tmpPath, path)
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}
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func LoadPNG(path string, bg color.RGBA) image.Image {
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var err error
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var file *os.File
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if file, err = os.Open(path); err != nil {
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return image.NewUniform(bg)
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}
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defer file.Close()
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reader := bufio.NewReader(file)
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var img image.Image
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if img, err = png.Decode(reader); err != nil {
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log.Printf("WARN: decoding '%s' failed: %s\n", path, err)
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return image.NewUniform(bg)
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}
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return img
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}
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func HashImage(img *image.RGBA) []byte {
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hash, _ := blake2b.New256(nil)
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w, h := img.Rect.Dx()*4, img.Rect.Dy()
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pos := img.PixOffset(img.Rect.Min.X, img.Rect.Min.Y)
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for ; h > 0; h, pos = h-1, pos+img.Stride {
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hash.Write(img.Pix[pos : pos+w])
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}
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return hash.Sum(nil)
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}
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func BackgroundImage(width, height int, bg color.RGBA) *image.RGBA {
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m := image.NewRGBA(image.Rect(0, 0, width, height))
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draw.Draw(m, m.Bounds(), &image.Uniform{bg}, image.Point{}, draw.Src)
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return m
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}
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