How to use parallel processing and concurrency for image manipulation in Go?

To use parallel processing and concurrency for image manipulation in Go, you can follow these steps:

Step 1: Import the required Go standard packages:

import (
    "image"
    "image/color"
    "image/jpeg"
    "os"
)

Step 2: Load the image file:

file, err := os.Open("input.jpg")
if err != nil {
    panic(err)
}
defer file.Close()

img, err := jpeg.Decode(file)
if err != nil {
    panic(err)
}

Step 3: Define the number of Goroutines (parallel routines) you want to use:

numGoroutines := 8

Step 4: Divide the image into smaller chunks based on the number of Goroutines:

width := img.Bounds().Size().X
height := img.Bounds().Size().Y

chunkHeight := height / numGoroutines
remainder := height % numGoroutines

type imageChunk struct {
    minY, maxY int
}
chunks := make([]imageChunk, numGoroutines)

startY := 0
for i := 0; i < numGoroutines; i++ {
    chunkHeightAdjusted := chunkHeight
    if i < remainder {
        chunkHeightAdjusted += 1
    }
    chunks[i] = imageChunk{minY: startY, maxY: startY + chunkHeightAdjusted}
    startY += chunkHeightAdjusted
}

Step 5: Define the image manipulation function that will be executed in parallel:

func manipulateImage(img image.Image, minY, maxY int) {
    for y := minY; y < maxY; y++ {
        for x := 0; x < width; x++ {
            // Perform image manipulation logic here, e.g., invert colors
            r, g, b, _ := img.At(x, y).RGBA()
            newColor := color.RGBA{
                R: uint8(255 - r/256),
                G: uint8(255 - g/256),
                B: uint8(255 - b/256),
                A: 255,
            }
            img.(*image.RGBA).Set(x, y, newColor)
        }
    }
}

Step 6: Launch multiple Goroutines to perform image manipulation in parallel:

var wg sync.WaitGroup

for i := 0; i < numGoroutines; i++ {
    wg.Add(1)
    go func(i int) {
        defer wg.Done()
        chunk := chunks[i]
        manipulateImage(img, chunk.minY, chunk.maxY)
    }(i)
}

wg.Wait() // Wait for all Goroutines to finish

Step 7: Save the modified image to file:

outputFile, err := os.Create("output.jpg")
if err != nil {
    panic(err)
}
defer outputFile.Close()

jpeg.Encode(outputFile, img, nil)

This example divides the image into smaller chunks and assigns each chunk to a separate Goroutine, allowing for parallel image manipulation. By using Goroutines and concurrency, you can efficiently process images in parallel and speed up the overall execution time.