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decode.go
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decode.go
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package images
import (
"bytes"
"errors"
"image"
"image/gif"
"image/jpeg"
"image/png"
"io"
"io/ioutil"
"net/http"
"os"
"regexp"
"time"
"unicode/utf8"
"golang.org/x/image/webp"
"github.com/ethereum/go-ethereum/log"
)
var (
htmlCommentRegex = regexp.MustCompile(`(?i)<!--([\\s\\S]*?)-->`)
svgRegex = regexp.MustCompile(`(?i)^\s*(?:<\?xml[^>]*>\s*)?(?:<!doctype svg[^>]*>\s*)?<svg[^>]*>[^*]*<\/svg>\s*$`)
)
// IsSVG returns true if the given buffer is a valid SVG image.
func IsSVG(buf []byte) bool {
var isBinary bool
if len(buf) < 24 {
isBinary = false
}
for i := 0; i < 14; i++ {
charCode, _ := utf8.DecodeRuneInString(string(buf[i]))
if charCode == 65533 || charCode <= 8 {
isBinary = true
}
}
return !isBinary && svgRegex.Match(htmlCommentRegex.ReplaceAll(buf, []byte{}))
}
func Decode(fileName string) (image.Image, error) {
file, err := os.Open(fileName)
if err != nil {
return nil, err
}
defer file.Close()
fb, err := prepareFileForDecode(file)
if err != nil {
return nil, err
}
return DecodeImageData(fb, file)
}
func DecodeFromURL(path string) (image.Image, error) {
client := http.Client{
Timeout: 5 * time.Second,
}
res, err := client.Get(path)
if err != nil {
return nil, err
}
defer func() {
if err := res.Body.Close(); err != nil {
log.Error("failed to close profile pic http request body", "err", err)
}
}()
if res.StatusCode >= 400 {
return nil, errors.New(http.StatusText(res.StatusCode))
}
bodyBytes, err := ioutil.ReadAll(res.Body)
if err != nil {
return nil, err
}
return DecodeImageData(bodyBytes, bytes.NewReader(bodyBytes))
}
func prepareFileForDecode(file *os.File) ([]byte, error) {
// Read the first 14 bytes, used for performing image type checks before parsing the image data
fb := make([]byte, 14)
_, err := file.Read(fb)
if err != nil {
return nil, err
}
// Reset the read cursor
_, err = file.Seek(0, 0)
if err != nil {
return nil, err
}
return fb, nil
}
func DecodeImageData(buf []byte, r io.Reader) (img image.Image, err error) {
switch GetType(buf) {
case JPEG:
img, err = jpeg.Decode(r)
case PNG:
img, err = png.Decode(r)
case GIF:
img, err = gif.Decode(r)
case WEBP:
img, err = webp.Decode(r)
case UNKNOWN:
fallthrough
default:
return nil, errors.New("unsupported file type")
}
if err != nil {
return nil, err
}
return img, nil
}
func GetType(buf []byte) ImageType {
switch {
case IsJpeg(buf):
return JPEG
case IsPng(buf):
return PNG
case IsGif(buf):
return GIF
case IsWebp(buf):
return WEBP
case IsIco(buf):
return ICO
default:
return UNKNOWN
}
}
func GetMimeType(buf []byte) (string, error) {
switch {
case IsJpeg(buf):
return "jpeg", nil
case IsPng(buf):
return "png", nil
case IsGif(buf):
return "gif", nil
case IsWebp(buf):
return "webp", nil
case IsIco(buf):
return "ico", nil
case IsSVG(buf):
return "svg", nil
default:
return "", errors.New("image format not supported")
}
}
func IsJpeg(buf []byte) bool {
return len(buf) > 2 &&
buf[0] == 0xFF &&
buf[1] == 0xD8 &&
buf[2] == 0xFF
}
func IsPng(buf []byte) bool {
return len(buf) > 3 &&
buf[0] == 0x89 && buf[1] == 0x50 &&
buf[2] == 0x4E && buf[3] == 0x47
}
func IsGif(buf []byte) bool {
return len(buf) > 2 &&
buf[0] == 0x47 && buf[1] == 0x49 && buf[2] == 0x46
}
func IsWebp(buf []byte) bool {
return len(buf) > 11 &&
buf[8] == 0x57 && buf[9] == 0x45 &&
buf[10] == 0x42 && buf[11] == 0x50
}
func IsIco(buf []byte) bool {
return len(buf) > 4 &&
buf[0] == 0 && buf[1] == 0 && buf[2] == 1 || buf[2] == 2 &&
buf[4] > 0
}
func GetImageDimensions(imgBytes []byte) (int, int, error) {
// Decode image bytes
img, _, err := image.Decode(bytes.NewReader(imgBytes))
if err != nil {
return 0, 0, err
}
// Get the image dimensions
bounds := img.Bounds()
width := bounds.Max.X - bounds.Min.X
height := bounds.Max.Y - bounds.Min.Y
return width, height, nil
}