media.go

package gouse

import (
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"image/jpeg"
	"image/png"
	"log"
	"os"
)

/* Canvas */

func CreateCanvas(size int, hexColor string) (*image.RGBA, error) {
	width, height := size, size
	bgColor, err := HexToRGBA(hexColor)
	if err != nil {
		log.Fatal(err)
	}
	background := image.NewRGBA(image.Rect(0, 0, width, height))
	draw.Draw(background, background.Bounds(), &image.Uniform{C: bgColor},
		image.Point{}, draw.Src)
	return background, err
}

/* Convert */

func HexToRGBA(hex string) (color.RGBA, error) {
	var (
		rgba             color.RGBA
		err              error
		errInvalidFormat = fmt.Errorf("invalid")
	)
	rgba.A = 0xff
	if hex[0] != '#' {
		return rgba, errInvalidFormat
	}
	hexToByte := func(b byte) byte {
		switch {
		case b >= '0' && b <= '9':
			return b - '0'
		case b >= 'a' && b <= 'f':
			return b - 'a' + 10
		case b >= 'A' && b <= 'F':
			return b - 'A' + 10
		}
		err = errInvalidFormat
		return 0
	}
	switch len(hex) {
	case 7:
		rgba.R = hexToByte(hex[1])<<4 + hexToByte(hex[2])
		rgba.G = hexToByte(hex[3])<<4 + hexToByte(hex[4])
		rgba.B = hexToByte(hex[5])<<4 + hexToByte(hex[6])
	case 4:
		rgba.R = hexToByte(hex[1]) * 17
		rgba.G = hexToByte(hex[2]) * 17
		rgba.B = hexToByte(hex[3]) * 17
	default:
		err = errInvalidFormat
	}
	return rgba, err
}

func formatError(message string, err error) error {
	return fmt.Errorf("%s: %v", message, err)
}

func PNGToJPG(input, output string) error {
	pngFile, err := os.Open(input)
	if err != nil {
		return formatError("Error opening PNG file", err)
	}
	defer pngFile.Close()

	pngImage, err := png.Decode(pngFile)
	if err != nil {
		return formatError("Error decoding PNG file", err)
	}

	jpegFile, err := os.Create(output)
	if err != nil {
		return formatError("Error creating JPEG file", err)
	}
	defer jpegFile.Close()

	err = jpeg.Encode(jpegFile, pngImage, nil)
	if err != nil {
		return formatError("Error encoding image to JPEG", err)
	}

	return nil
}