137 lines
2.5 KiB
Go
137 lines
2.5 KiB
Go
package images
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import (
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"errors"
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"image"
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"image/gif"
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"image/jpeg"
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"image/png"
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"io"
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"os"
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"golang.org/x/image/webp"
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)
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func Get(fileName string) (image.Image, error) {
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file, err := os.Open(fileName)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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fb, err := prepareFileForDecode(file)
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if err != nil {
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return nil, err
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}
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return decodeImageData(fb, file)
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}
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func prepareFileForDecode(file *os.File) ([]byte, error) {
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// Read the first 14 bytes, used for performing image type checks before parsing the image data
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fb := make([]byte, 14)
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_, err := file.Read(fb)
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if err != nil {
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return nil, err
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}
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// Reset the read cursor
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_, err = file.Seek(0, 0)
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if err != nil {
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return nil, err
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}
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return fb, nil
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}
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func decodeImageData(buf []byte, r io.Reader) (img image.Image, err error) {
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switch GetFileType(buf) {
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case JPEG:
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img, err = jpeg.Decode(r)
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case PNG:
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img, err = png.Decode(r)
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case GIF:
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img, err = gif.Decode(r)
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case WEBP:
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img, err = webp.Decode(r)
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case UNKNOWN:
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fallthrough
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default:
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return nil, errors.New("unsupported file type")
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}
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if err != nil {
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return nil, err
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}
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return img, nil
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}
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func GetFileType(buf []byte) FileType {
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switch {
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case isJpeg(buf):
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return JPEG
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case isPng(buf):
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return PNG
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case isGif(buf):
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return GIF
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case isWebp(buf):
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return WEBP
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default:
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return UNKNOWN
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}
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}
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func isJpeg(buf []byte) bool {
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return len(buf) > 2 &&
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buf[0] == 0xFF &&
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buf[1] == 0xD8 &&
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buf[2] == 0xFF
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}
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func isPng(buf []byte) bool {
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return len(buf) > 3 &&
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buf[0] == 0x89 && buf[1] == 0x50 &&
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buf[2] == 0x4E && buf[3] == 0x47
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}
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func isGif(buf []byte) bool {
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return len(buf) > 2 &&
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buf[0] == 0x47 && buf[1] == 0x49 && buf[2] == 0x46
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}
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func isWebp(buf []byte) bool {
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return len(buf) > 11 &&
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buf[8] == 0x57 && buf[9] == 0x45 &&
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buf[10] == 0x42 && buf[11] == 0x50
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}
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func RenderAndMakeFile(img image.Image, imgDetail *Details) error {
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out, err := os.Create(imgDetail.FileName)
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if err != nil {
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return err
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}
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defer out.Close()
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err = Render(out, img, imgDetail)
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if err != nil {
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return err
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}
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fi, _ := out.Stat()
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imgDetail.SizeFile = fi.Size()
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return nil
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}
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func Render(w io.Writer, img image.Image, imgDetail *Details) error {
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// Currently a wrapper for renderJpeg, but this function is useful if multiple render formats are needed
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return renderJpeg(w, img, imgDetail)
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}
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func renderJpeg(w io.Writer, m image.Image, imgDetail *Details) error {
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o := new(jpeg.Options)
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o.Quality = imgDetail.Quality
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return jpeg.Encode(w, m, o)
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}
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