imgo/util.go

package imgo

import (
	"fmt"
	"golang.org/x/image/bmp"
	"golang.org/x/image/tiff"
	"golang.org/x/image/webp"
	"image"
	"image/color"
	"image/draw"
	"image/jpeg"
	"image/png"
	"io"
)

// GetImageType returns the extension, mimetype and corresponding decoder function of the image.
// It judges the image by its first few bytes called magic number.
func GetImageType(bytes []byte) (ext string, mimetype string, decoder func(r io.Reader) (image.Image, error), err error) {
	if len(bytes) < 2 {
		err = ErrSourceImageNotSupport
		return
	}

	if bytes[0] == 0xFF && bytes[1] == 0xD8 {
		ext = "jpg"
		mimetype = "image/jpeg"
		decoder = jpeg.Decode
	}

	if len(bytes) >= 4 && bytes[0] == 0x89 && bytes[1] == 0x50 && bytes[2] == 0x4E && bytes[3] == 0x47 {
		ext = "png"
		mimetype = "image/png"
		decoder = png.Decode
	}

	if bytes[0] == 0x42 && bytes[1] == 0x4D {
		ext = "bmp"
		mimetype = "image/x-ms-bmp"
		decoder = bmp.Decode
	}

	if (bytes[0] == 0x49 && bytes[1] == 0x49) || (bytes[0] == 0x4D && bytes[1] == 0x4D) {
		ext = "tiff"
		mimetype = "image/tiff"
		decoder = tiff.Decode
	}

	if bytes[0] == 0x52 && bytes[1] == 0x49 {
		ext = "webp"
		mimetype = "image/webp"
		decoder = webp.Decode
	}

	/*if bytes[0] == 0x47 && bytes[1] == 0x49 && bytes[2] == 0x46 && bytes[3] == 0x38 {
	      ext = "gif"
	      mimetype = "image/gif"
	  }

	  if bytes[0] == 0x00 && bytes[1] == 0x00 && (bytes[2] == 0x01 || bytes[2] == 0x02) && bytes[3] == 0x00 {
	      ext = "ico"
	      mimetype = "image/x-icon"
	  }*/

	if ext == "" {
		err = ErrSourceImageNotSupport
	}

	return
}

// Color2Hex converts a color.Color to its hex string representation.
func Color2Hex(c color.Color) string {
	r, g, b, _ := c.RGBA()
	return fmt.Sprintf("#%02X%02X%02X", uint8(r>>8), uint8(g>>8), uint8(b>>8))
}

// Image2RGBA converts an image to RGBA.
func Image2RGBA(img image.Image) *image.RGBA {
	rgba := image.NewRGBA(img.Bounds())
	draw.Draw(rgba, rgba.Bounds(), img, img.Bounds().Min, draw.Over)
	return rgba
}