Golang: Creating Images and Drawing — Simply Explained (Part 1)

Photo by Eddy Klaus on Unsplash

Understanding the key elements of the framework

Interface image.Image

  1. Function that returns a color model — this color model is how the data translating to pixels are stored in binary format;
  2. Function that returns the bounding rectangle — this represents the size of the rectangle that forms the bounding geometry of the image; and
  3. Function that returns the color.Color at the input x and y integer coordinates.
type Image interface {

ColorModel() color.Model

Bounds() Rectangle

At(x, y int) color.Color
}

Interface draw.Image

type Image interface {
image.Image
Set(x, y int, c color.Color)
}

Actual Structs

  • Gray —8-bit greyscale
  • Gray16– 16–bit greyscale
  • CMYK
  • Paletted
  • RGBA — most commonly know color model of red, green, blue and alpha channels, each 8 bits
  • NRGBA — non-alpha-premultiplied 32-bit color (each channel is 8-bit)
  • NRGBA64 — non-alpha-premultiplied 64-bit color (each channel is 16-bit)
  • NYCbCrA — non-alpha-premultiplied Y’CbCr-with-alpha (8-bit for each of Luma and the two chroma components; JPEG, VP8, MPEG codecs etc use this color model)
  • Alpha — a single channel (alpha) 8-bit
  • Alpha16 — a single channel (alpha) 16-bit

Now that I know about the structs, but how do you get the structs then?

import _ "image/jpeg" //will call the init() function of the package
//thus enabling working with jpeg file
func OpenImage(path string) (image.Image, error) {
f, err := os.Open(path)
if err != nil {
fmt.Println(err)
return nil, err
}
defer f.Close()
img, format, err := image.Decode(f)
if err != nil {
e := fmt.Errorf("error in decoding: %w", err)
return nil, e
}
if format != "jpeg" && format != "png" {
e := fmt.Errorf("error in image format - not jpeg")
return nil, e
}
return img, nil
}
func GetImageTensor(img image.Image) (pixels [][]color.Color) {
size := img.Bounds().Size()
for i := 0; i < size.X; i++ {
var y []color.Color
for j := 0; j < size.Y; j++ {
y = append(y, img.At(i, j))
}
pixels = append(pixels, y) // 2 by 2 slices where
//each contains a color.color
}
return
}
func ConvertGreyScale(pixels *[][]color.Color) image.Image {        p := *pixels
wg := sync.WaitGroup{}
rect := image.Rect(0, 0, len(p), len(p[0]))
newImage := image.NewRGBA(rect)
for x := 0; x < len(p); x++ {
for y := 0; y < len(p[0]); y++ {
wg.Add(1)
go func(x, y int) {
pix := p[x][y]
originalColor, ok := color.RGBAModel.Convert(pix).(color.RGBA)
if !ok {
log.Fatalf("color.color conversion went wrong")
}
grey := uint8(float64(originalColor.R)*0.21 + float64(originalColor.G)*0.72 + float64(originalColor.B)*0.07)
col := color.RGBA{
grey,
grey,
grey,
originalColor.A,
}
newImage.Set(x, y, col)
wg.Done()
}(x, y)
}
}
return newImage
}
Original image (courtesy of CC) and the grayscaled image
Example of the draw library where you can place your own QR code through compositing

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Writing to soothe the soul, programming to achieve flow

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Writing to soothe the soul, programming to achieve flow

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