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// Package imaging provides basic image manipulation functions (resize, rotate, flip, crop, etc.).
// This package is based on the standard Go image package and works best along with it.
//
// Image manipulation functions provided by the package take any image type
// that implements `image.Image` interface as an input, and return a new image of
// `*image.NRGBA` type (32bit RGBA colors, not premultiplied by alpha).
package imaging
import (
"errors"
"image"
"image/color"
"image/gif"
"image/jpeg"
"image/png"
"io"
"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 (
// ErrUnsupportedFormat means the given image format (or file extension) is unsupported.
ErrUnsupportedFormat = errors.New("imaging: unsupported image format")
)
// Decode reads an image from r.
func Decode(r io.Reader) (image.Image, error) {
img, _, err := image.Decode(r)
if err != nil {
return nil, err
}
return toNRGBA(img), nil
}
// Open loads an image from file
func Open(filename string) (image.Image, error) {
file, err := os.Open(filename)
if err != nil {
return nil, err
}
defer file.Close()
img, err := Decode(file)
return img, err
}
// 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) error {
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: 95})
} else {
err = jpeg.Encode(w, img, &jpeg.Options{Quality: 95})
}
case PNG:
err = png.Encode(w, img)
case GIF:
err = gif.Encode(w, img, &gif.Options{NumColors: 256})
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.
func Save(img image.Image, filename string) (err error) {
formats := map[string]Format{
".jpg": JPEG,
".jpeg": JPEG,
".png": PNG,
".tif": TIFF,
".tiff": TIFF,
".bmp": BMP,
".gif": GIF,
}
ext := strings.ToLower(filepath.Ext(filename))
f, ok := formats[ext]
if !ok {
return ErrUnsupportedFormat
}
file, err := os.Create(filename)
if err != nil {
return err
}
defer file.Close()
return Encode(file, img, f)
}
// New creates a new image with the specified width and height, and fills it with the specified color.
func New(width, height int, fillColor color.Color) *image.NRGBA {
if width <= 0 || height <= 0 {
return &image.NRGBA{}
}
dst := image.NewNRGBA(image.Rect(0, 0, width, height))
c := color.NRGBAModel.Convert(fillColor).(color.NRGBA)
if c.R == 0 && c.G == 0 && c.B == 0 && c.A == 0 {
return dst
}
cs := []uint8{c.R, c.G, c.B, c.A}
// fill the first row
for x := 0; x < width; x++ {
copy(dst.Pix[x*4:(x+1)*4], cs)
}
// copy the first row to other rows
for y := 1; y < height; y++ {
copy(dst.Pix[y*dst.Stride:y*dst.Stride+width*4], dst.Pix[0:width*4])
}
return dst
}
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