rotate-fixed-optimized.go

package filters

import (
	"fmt"
	"image/color"
	"math"
	"runtime"
	"sync"
	"time"

	"go-image-processing/constants"
	"go-image-processing/utilities"
)

func RotateFixed(path string, angle uint) {
	if angle != constants.ROTATE_FIXED_90 &&
		angle != constants.ROTATE_FIXED_180 &&
		angle != constants.ROTATE_FIXED_270 {
		angle = constants.ROTATE_FIXED_90
	}
	img, format, openMS, convertMS := open(path)
	now := math.Round(float64(time.Now().UnixNano()) / 1000000)
	width, height := img.Rect.Max.X, img.Rect.Max.Y
	gridWidth, gridHeight := width, height
	if angle != constants.ROTATE_FIXED_180 {
		gridWidth, gridHeight = height, width
	}
	destination := utilities.CreateGrid(gridWidth, gridHeight)

	pixLen := len(img.Pix)
	threads := runtime.NumCPU()
	pixPerThread := getPixPerThread(pixLen, threads)

	var wg sync.WaitGroup

	processing := func(thread int) {
		defer wg.Done()
		startIndex := pixPerThread * thread
		endIndex := clampMax(startIndex+pixPerThread, pixLen)
		for i := startIndex; i < endIndex; i += 4 {
			x, y := getCoordinates(i/4, width)
			dx, dy := y, x
			if angle == constants.ROTATE_FIXED_90 {
				dx = height - y - 1
			}
			if angle == constants.ROTATE_FIXED_180 {
				dx, dy = width-x-1, height-y-1
			}
			if angle == constants.ROTATE_FIXED_270 {
				dy = width - x - 1
			}
			destination[dx][dy] = color.RGBA{
				img.Pix[i],
				img.Pix[i+1],
				img.Pix[i+2],
				img.Pix[i+3],
			}
		}
	}

	for t := 0; t < threads; t += 1 {
		wg.Add(1)
		go processing(t)
	}

	wg.Wait()

	processMS := int(math.Round(float64(time.Now().UnixNano())/1000000) - now)
	saveMS := utilities.SaveFile(
		fmt.Sprintf(`file-%d.%s`, time.Now().Unix(), format),
		format,
		destination,
	)
	sum := openMS + convertMS + processMS + saveMS
	println("open", openMS, "convert", convertMS, "process", processMS, "save", saveMS, "sum", sum)
}