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package imaging
import (
"encoding/binary"
"errors"
"image"
"image/draw"
"image/gif"
"image/jpeg"
"image/png"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
"golang.org/x/image/bmp"
"golang.org/x/image/tiff"
)
// Format is an image file format.
type Format int
// Image file formats.
const (
JPEG Format = iota
PNG
GIF
TIFF
BMP
)
func (f Format) String() string {
switch f {
case JPEG:
return "JPEG"
case PNG:
return "PNG"
case GIF:
return "GIF"
case TIFF:
return "TIFF"
case BMP:
return "BMP"
default:
return "Unsupported"
}
}
var formatFromExt = map[string]Format{
"jpg": JPEG,
"jpeg": JPEG,
"png": PNG,
"tif": TIFF,
"tiff": TIFF,
"bmp": BMP,
"gif": GIF,
}
// FormatFromExtension parses image format from extension:
// "jpg" (or "jpeg"), "png", "gif", "tif" (or "tiff") and "bmp" are supported.
func FormatFromExtension(ext string) (Format, error) {
if f, ok := formatFromExt[strings.ToLower(strings.TrimPrefix(ext, "."))]; ok {
return f, nil
}
return -1, ErrUnsupportedFormat
}
// FormatFromFilename parses image format from filename extension:
// "jpg" (or "jpeg"), "png", "gif", "tif" (or "tiff") and "bmp" are supported.
func FormatFromFilename(filename string) (Format, error) {
ext := filepath.Ext(filename)
return FormatFromExtension(ext)
}
var (
// ErrUnsupportedFormat means the given image format (or file extension) is unsupported.
ErrUnsupportedFormat = errors.New("imaging: unsupported image format")
)
type fileSystem interface {
Create(string) (io.WriteCloser, error)
Open(string) (io.ReadCloser, error)
}
type localFS struct{}
func (localFS) Create(name string) (io.WriteCloser, error) { return os.Create(name) }
func (localFS) Open(name string) (io.ReadCloser, error) { return os.Open(name) }
var fs fileSystem = localFS{}
type decodeConfig struct {
autoOrientation bool
}
var defaultDecodeConfig = decodeConfig{
autoOrientation: false,
}
// DecodeOption sets an optional parameter for the Decode and Open functions.
type DecodeOption func(*decodeConfig)
// AutoOrientation returns a DecodeOption that sets the auto-orientation mode.
// If auto-orientation is enabled, the image will be transformed after decoding
// according to the EXIF orientation tag (if present). By default it's disabled.
func AutoOrientation(enabled bool) DecodeOption {
return func(c *decodeConfig) {
c.autoOrientation = enabled
}
}
// Decode reads an image from r.
func Decode(r io.Reader, opts ...DecodeOption) (image.Image, error) {
cfg := defaultDecodeConfig
for _, option := range opts {
option(&cfg)
}
if !cfg.autoOrientation {
img, _, err := image.Decode(r)
return img, err
}
var orient orientation
pr, pw := io.Pipe()
r = io.TeeReader(r, pw)
done := make(chan struct{})
go func() {
defer close(done)
orient = readOrientation(pr)
io.Copy(ioutil.Discard, pr)
}()
img, _, err := image.Decode(r)
pw.Close()
<-done
if err != nil {
return nil, err
}
return fixOrientation(img, orient), nil
}
// Open loads an image from file.
//
// Examples:
//
// // Load an image from file.
// img, err := imaging.Open("test.jpg")
//
// // Load an image and transform it depending on the EXIF orientation tag (if present).
// img, err := imaging.Open("test.jpg", imaging.AutoOrientation(true))
//
func Open(filename string, opts ...DecodeOption) (image.Image, error) {
file, err := fs.Open(filename)
if err != nil {
return nil, err
}
defer file.Close()
return Decode(file, opts...)
}
type encodeConfig struct {
jpegQuality int
gifNumColors int
gifQuantizer draw.Quantizer
gifDrawer draw.Drawer
pngCompressionLevel png.CompressionLevel
}
var defaultEncodeConfig = encodeConfig{
jpegQuality: 95,
gifNumColors: 256,
gifQuantizer: nil,
gifDrawer: nil,
pngCompressionLevel: png.DefaultCompression,
}
// EncodeOption sets an optional parameter for the Encode and Save functions.
type EncodeOption func(*encodeConfig)
// JPEGQuality returns an EncodeOption that sets the output JPEG quality.
// Quality ranges from 1 to 100 inclusive, higher is better. Default is 95.
func JPEGQuality(quality int) EncodeOption {
return func(c *encodeConfig) {
c.jpegQuality = quality
}
}
// GIFNumColors returns an EncodeOption that sets the maximum number of colors
// used in the GIF-encoded image. It ranges from 1 to 256. Default is 256.
func GIFNumColors(numColors int) EncodeOption {
return func(c *encodeConfig) {
c.gifNumColors = numColors
}
}
// GIFQuantizer returns an EncodeOption that sets the quantizer that is used to produce
// a palette of the GIF-encoded image.
func GIFQuantizer(quantizer draw.Quantizer) EncodeOption {
return func(c *encodeConfig) {
c.gifQuantizer = quantizer
}
}
// GIFDrawer returns an EncodeOption that sets the drawer that is used to convert
// the source image to the desired palette of the GIF-encoded image.
func GIFDrawer(drawer draw.Drawer) EncodeOption {
return func(c *encodeConfig) {
c.gifDrawer = drawer
}
}
// PNGCompressionLevel returns an EncodeOption that sets the compression level
// of the PNG-encoded image. Default is png.DefaultCompression.
func PNGCompressionLevel(level png.CompressionLevel) EncodeOption {
return func(c *encodeConfig) {
c.pngCompressionLevel = level
}
}
// Encode writes the image img to w in the specified format (JPEG, PNG, GIF, TIFF or BMP).
func Encode(w io.Writer, img image.Image, format Format, opts ...EncodeOption) error {
cfg := defaultEncodeConfig
for _, option := range opts {
option(&cfg)
}
var err error
switch format {
case JPEG:
var rgba *image.RGBA
if nrgba, ok := img.(*image.NRGBA); ok {
if nrgba.Opaque() {
rgba = &image.RGBA{
Pix: nrgba.Pix,
Stride: nrgba.Stride,
Rect: nrgba.Rect,
}
}
}
if rgba != nil {
err = jpeg.Encode(w, rgba, &jpeg.Options{Quality: cfg.jpegQuality})
} else {
err = jpeg.Encode(w, img, &jpeg.Options{Quality: cfg.jpegQuality})
}
case PNG:
enc := png.Encoder{CompressionLevel: cfg.pngCompressionLevel}
err = enc.Encode(w, img)
case GIF:
err = gif.Encode(w, img, &gif.Options{
NumColors: cfg.gifNumColors,
Quantizer: cfg.gifQuantizer,
Drawer: cfg.gifDrawer,
})
case TIFF:
err = tiff.Encode(w, img, &tiff.Options{Compression: tiff.Deflate, Predictor: true})
case BMP:
err = bmp.Encode(w, img)
default:
err = ErrUnsupportedFormat
}
return err
}
// Save saves the image to file with the specified filename.
// The format is determined from the filename extension:
// "jpg" (or "jpeg"), "png", "gif", "tif" (or "tiff") and "bmp" are supported.
//
// Examples:
//
// // Save the image as PNG.
// err := imaging.Save(img, "out.png")
//
// // Save the image as JPEG with optional quality parameter set to 80.
// err := imaging.Save(img, "out.jpg", imaging.JPEGQuality(80))
//
func Save(img image.Image, filename string, opts ...EncodeOption) (err error) {
f, err := FormatFromFilename(filename)
if err != nil {
return err
}
file, err := fs.Create(filename)
if err != nil {
return err
}
defer func() {
cerr := file.Close()
if err == nil {
err = cerr
}
}()
return Encode(file, img, f, opts...)
}
// orientation is an EXIF flag that specifies the transformation
// that should be applied to image to display it correctly.
type orientation int
const (
orientationUnspecified = 0
orientationNormal = 1
orientationFlipH = 2
orientationRotate180 = 3
orientationFlipV = 4
orientationTranspose = 5
orientationRotate270 = 6
orientationTransverse = 7
orientationRotate90 = 8
)
// readOrientation tries to read the orientation EXIF flag from image data in r.
// If the EXIF data block is not found or the orientation flag is not found
// or any other error occures while reading the data, it returns the
// orientationUnspecified (0) value.
func readOrientation(r io.Reader) orientation {
const (
markerSOI = 0xffd8
markerAPP1 = 0xffe1
exifHeader = 0x45786966
byteOrderBE = 0x4d4d
byteOrderLE = 0x4949
orientationTag = 0x0112
)
// Check if JPEG SOI marker is present.
var soi uint16
if err := binary.Read(r, binary.BigEndian, &soi); err != nil {
return orientationUnspecified
}
if soi != markerSOI {
return orientationUnspecified // Missing JPEG SOI marker.
}
// Find JPEG APP1 marker.
for {
var marker, size uint16
if err := binary.Read(r, binary.BigEndian, &marker); err != nil {
return orientationUnspecified
}
if err := binary.Read(r, binary.BigEndian, &size); err != nil {
return orientationUnspecified
}
if marker>>8 != 0xff {
return orientationUnspecified // Invalid JPEG marker.
}
if marker == markerAPP1 {
break
}
if size < 2 {
return orientationUnspecified // Invalid block size.
}
if _, err := io.CopyN(ioutil.Discard, r, int64(size-2)); err != nil {
return orientationUnspecified
}
}
// Check if EXIF header is present.
var header uint32
if err := binary.Read(r, binary.BigEndian, &header); err != nil {
return orientationUnspecified
}
if header != exifHeader {
return orientationUnspecified
}
if _, err := io.CopyN(ioutil.Discard, r, 2); err != nil {
return orientationUnspecified
}
// Read byte order information.
var (
byteOrderTag uint16
byteOrder binary.ByteOrder
)
if err := binary.Read(r, binary.BigEndian, &byteOrderTag); err != nil {
return orientationUnspecified
}
switch byteOrderTag {
case byteOrderBE:
byteOrder = binary.BigEndian
case byteOrderLE:
byteOrder = binary.LittleEndian
default:
return orientationUnspecified // Invalid byte order flag.
}
if _, err := io.CopyN(ioutil.Discard, r, 2); err != nil {
return orientationUnspecified
}
// Skip the EXIF offset.
var offset uint32
if err := binary.Read(r, byteOrder, &offset); err != nil {
return orientationUnspecified
}
if offset < 8 {
return orientationUnspecified // Invalid offset value.
}
if _, err := io.CopyN(ioutil.Discard, r, int64(offset-8)); err != nil {
return orientationUnspecified
}
// Read the number of tags.
var numTags uint16
if err := binary.Read(r, byteOrder, &numTags); err != nil {
return orientationUnspecified
}
// Find the orientation tag.
for i := 0; i < int(numTags); i++ {
var tag uint16
if err := binary.Read(r, byteOrder, &tag); err != nil {
return orientationUnspecified
}
if tag != orientationTag {
if _, err := io.CopyN(ioutil.Discard, r, 10); err != nil {
return orientationUnspecified
}
continue
}
if _, err := io.CopyN(ioutil.Discard, r, 6); err != nil {
return orientationUnspecified
}
var val uint16
if err := binary.Read(r, byteOrder, &val); err != nil {
return orientationUnspecified
}
if val < 1 || val > 8 {
return orientationUnspecified // Invalid tag value.
}
return orientation(val)
}
return orientationUnspecified // Missing orientation tag.
}
// fixOrientation applies a transform to img corresponding to the given orientation flag.
func fixOrientation(img image.Image, o orientation) image.Image {
switch o {
case orientationNormal:
case orientationFlipH:
img = FlipH(img)
case orientationFlipV:
img = FlipV(img)
case orientationRotate90:
img = Rotate90(img)
case orientationRotate180:
img = Rotate180(img)
case orientationRotate270:
img = Rotate270(img)
case orientationTranspose:
img = Transpose(img)
case orientationTransverse:
img = Transverse(img)
}
return img
}
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