seaweedfs/go/images/orientation.go

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2014-05-15 07:30:46 +00:00
package images
import (
"bytes"
"github.com/rwcarlsen/goexif/exif"
"image"
"image/draw"
"image/jpeg"
"log"
)
//many code is copied from http://camlistore.org/pkg/images/images.go
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func FixJpgOrientation(data []byte) (oriented []byte) {
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ex, err := exif.Decode(bytes.NewReader(data))
if err != nil {
return data
}
tag, err := ex.Get(exif.Orientation)
if err != nil {
return data
}
angle := 0
flipMode := FlipDirection(0)
orient := tag.Int(0)
switch orient {
case topLeftSide:
// do nothing
return data
case topRightSide:
flipMode = 2
case bottomRightSide:
angle = 180
case bottomLeftSide:
angle = 180
flipMode = 2
case leftSideTop:
angle = -90
flipMode = 2
case rightSideTop:
angle = -90
case rightSideBottom:
angle = 90
flipMode = 2
case leftSideBottom:
angle = 90
}
if srcImage, _, err := image.Decode(bytes.NewReader(data)); err == nil {
dstImage := flip(rotate(srcImage, angle), flipMode)
var buf bytes.Buffer
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jpeg.Encode(&buf, dstImage, nil)
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return buf.Bytes()
}
return data
}
// Exif Orientation Tag values
// http://sylvana.net/jpegcrop/exif_orientation.html
const (
topLeftSide = 1
topRightSide = 2
bottomRightSide = 3
bottomLeftSide = 4
leftSideTop = 5
rightSideTop = 6
rightSideBottom = 7
leftSideBottom = 8
)
// The FlipDirection type is used by the Flip option in DecodeOpts
// to indicate in which direction to flip an image.
type FlipDirection int
// FlipVertical and FlipHorizontal are two possible FlipDirections
// values to indicate in which direction an image will be flipped.
const (
FlipVertical FlipDirection = 1 << iota
FlipHorizontal
)
type DecodeOpts struct {
// Rotate specifies how to rotate the image.
// If nil, the image is rotated automatically based on EXIF metadata.
// If an int, Rotate is the number of degrees to rotate
// counter clockwise and must be one of 0, 90, -90, 180, or
// -180.
Rotate interface{}
// Flip specifies how to flip the image.
// If nil, the image is flipped automatically based on EXIF metadata.
// Otherwise, Flip is a FlipDirection bitfield indicating how to flip.
Flip interface{}
}
func rotate(im image.Image, angle int) image.Image {
var rotated *image.NRGBA
// trigonometric (i.e counter clock-wise)
switch angle {
case 90:
newH, newW := im.Bounds().Dx(), im.Bounds().Dy()
rotated = image.NewNRGBA(image.Rect(0, 0, newW, newH))
for y := 0; y < newH; y++ {
for x := 0; x < newW; x++ {
rotated.Set(x, y, im.At(newH-1-y, x))
}
}
case -90:
newH, newW := im.Bounds().Dx(), im.Bounds().Dy()
rotated = image.NewNRGBA(image.Rect(0, 0, newW, newH))
for y := 0; y < newH; y++ {
for x := 0; x < newW; x++ {
rotated.Set(x, y, im.At(y, newW-1-x))
}
}
case 180, -180:
newW, newH := im.Bounds().Dx(), im.Bounds().Dy()
rotated = image.NewNRGBA(image.Rect(0, 0, newW, newH))
for y := 0; y < newH; y++ {
for x := 0; x < newW; x++ {
rotated.Set(x, y, im.At(newW-1-x, newH-1-y))
}
}
default:
return im
}
return rotated
}
// flip returns a flipped version of the image im, according to
// the direction(s) in dir.
// It may flip the imput im in place and return it, or it may allocate a
// new NRGBA (if im is an *image.YCbCr).
func flip(im image.Image, dir FlipDirection) image.Image {
if dir == 0 {
return im
}
ycbcr := false
var nrgba image.Image
dx, dy := im.Bounds().Dx(), im.Bounds().Dy()
di, ok := im.(draw.Image)
if !ok {
if _, ok := im.(*image.YCbCr); !ok {
log.Printf("failed to flip image: input does not satisfy draw.Image")
return im
}
// because YCbCr does not implement Set, we replace it with a new NRGBA
ycbcr = true
nrgba = image.NewNRGBA(image.Rect(0, 0, dx, dy))
di, ok = nrgba.(draw.Image)
if !ok {
log.Print("failed to flip image: could not cast an NRGBA to a draw.Image")
return im
}
}
if dir&FlipHorizontal != 0 {
for y := 0; y < dy; y++ {
for x := 0; x < dx/2; x++ {
old := im.At(x, y)
di.Set(x, y, im.At(dx-1-x, y))
di.Set(dx-1-x, y, old)
}
}
}
if dir&FlipVertical != 0 {
for y := 0; y < dy/2; y++ {
for x := 0; x < dx; x++ {
old := im.At(x, y)
di.Set(x, y, im.At(x, dy-1-y))
di.Set(x, dy-1-y, old)
}
}
}
if ycbcr {
return nrgba
}
return im
}