108 lines
2.9 KiB
Go
108 lines
2.9 KiB
Go
/*
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Copyright © 2022 NAME HERE <EMAIL ADDRESS>
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*/
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package cmd
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import (
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"image"
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"image/color"
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"image/jpeg"
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_ "image/png"
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"log"
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"os"
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"github.com/spf13/cobra"
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"golang.org/x/image/draw"
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)
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// convertCmd represents the convert command
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var convertCmd = &cobra.Command{
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Use: "convert",
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Short: "A brief description of your command",
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Long: `A longer description that spans multiple lines and likely contains examples
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and usage of using your command. For example:
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Cobra is a CLI library for Go that empowers applications.
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This application is a tool to generate the needed files
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to quickly create a Cobra application.`,
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Run: func(cmd *cobra.Command, args []string) {
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width, _ := cmd.Flags().GetInt("width")
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height, _ := cmd.Flags().GetInt("height")
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convertImage(width, height)
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},
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}
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func init() {
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rootCmd.AddCommand(convertCmd)
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convertCmd.Flags().Int("width", 540, "Target width")
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convertCmd.Flags().Int("height", 960, "Target height")
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}
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// Returns a new Rectangle that is resized and centered in `dst`
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func fitRectInto(src *image.Rectangle, dst *image.Rectangle) image.Rectangle {
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var targetWidth int
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var targetHeight int
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var scale float64
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srcRatio := float64(src.Max.X) / float64(src.Max.Y)
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dstRatio := float64(dst.Max.X) / float64(dst.Max.Y)
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if srcRatio < dstRatio {
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// center horizontally, scale vertically
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scale = float64(dst.Max.Y) / float64(src.Max.Y)
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} else {
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// center vertically, scale horizontally
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scale = float64(dst.Max.X) / float64(src.Max.X)
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}
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targetWidth = int(float64(src.Max.X) * scale)
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targetHeight = int(float64(src.Max.Y) * scale)
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targetX := (dst.Max.X - targetWidth) / 2
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targetY := (dst.Max.Y - targetHeight) / 2
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return image.Rect(targetX, targetY, targetWidth+targetX, targetHeight+targetY)
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}
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func convertImage(width int, height int) {
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// for now, we're reading a predefined input file
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input, err := os.Open("cat.jpg")
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if err != nil {
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log.Fatalf("Error opening file: %v", err)
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}
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defer input.Close()
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// … and writing to a predefined output file
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output, err := os.OpenFile("cat_resized.epd", os.O_RDWR|os.O_CREATE, 0644)
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if err != nil {
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log.Fatalf("Error writing output file: %v", err)
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}
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defer output.Close()
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src, _ := jpeg.Decode(input)
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dst := image.NewGray(image.Rect(0, 0, width, height))
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srcBounds := src.Bounds()
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targetRect := fitRectInto(&srcBounds, &dst.Rect)
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draw.Draw(dst, dst.Bounds(), &image.Uniform{color.White}, image.ZP, draw.Src)
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draw.CatmullRom.Scale(dst, targetRect, src, src.Bounds(), draw.Over, nil)
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// the actual conversion works by packing two nibbles together in a byte
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var result = make([]byte, (width*height+1)/2)
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for i, p := range dst.Pix {
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res := uint8((uint16(p) + 8) / 16)
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if i%2 == 0 {
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result[i/2] = (res << 4)
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} else {
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// note that integer division makes sure we're writing at the same
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// index for odd and even indices
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result[i/2] = result[i/2] | res
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}
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}
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output.Write(result)
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}
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