calc downsize of video resolution

calc_downsize.go

package main

import "fmt"

// Calculates scaling factors using old and new image dimensions.
func calcFactors(width, height uint, oldWidth, oldHeight float64) (scaleX, scaleY float64) {
	if width == 0 {
		if height == 0 {
			scaleX = 1.0
			scaleY = 1.0
		} else {
			scaleY = oldHeight / float64(height)
			scaleX = scaleY
		}
	} else {
		scaleX = oldWidth / float64(width)
		if height == 0 {
			scaleY = scaleX
		} else {
			scaleY = oldHeight / float64(height)
		}
	}
	return
}

func resize(width, height uint, orgWidth, orgHeight int) (w, h int) {
	scaleX, scaleY := calcFactors(width, height, float64(orgWidth), float64(orgHeight))
	if width == 0 {
		width = uint(float64(orgWidth) / scaleX)
		if width%2 != 0 {
			width++
		}
	}
	if height == 0 {
		height = uint(float64(orgHeight) / scaleY)
		if height%2 != 0 {
			height++
		}
	}

	return int(width), int(height)
}

func main() {
	type Resolution struct {
		width  int
		height int
	}
	// res169List := []Resolution{{3840, 2160}, {2560, 1440}, {1920, 1080},
	// 	{1280, 720}, {960, 540}, {854, 480}, {640, 360}, {512, 288}}

	// res916List := []Resolution{{2160, 3840}, {1440, 2560}, {1080, 1920},
	// 	{720, 1280}, {540, 960}, {480, 854}, {360, 640}, {288, 512}}

	res43List := []Resolution{{2048, 1536}, {1600, 1200}, {1280, 960},
		{800, 600}, {640, 480}, {512, 384}, {480, 360}, {400, 300}, {320, 240}}

	res34List := []Resolution{{1536, 2048}, {1200, 1600}, {960, 1280},
		{600, 800}, {480, 640}, {384, 512}, {360, 480}, {300, 400}, {240, 320}}

	for _, item := range res43List {
		var w, h int
		input := item.height
		fmt.Printf("Org    %d x %d\n", item.width, item.height)
		switch {
		case input > 1080:
			w, h = resize(0, 1080, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(0, 480, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 720:
			w, h = resize(0, 720, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(0, 480, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 480:
			w, h = resize(0, 480, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(0, 360, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 360:
			w, h = resize(0, 360, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		}
		fmt.Printf("\n")
	}
	fmt.Printf("========================\n")
	for _, item := range res34List {
		var w, h int
		input := item.width
		fmt.Printf("Org    %d x %d\n", item.width, item.height)
		switch {
		case input > 1080:
			w, h = resize(1080, 0, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(480, 0, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 720:
			w, h = resize(720, 0, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(480, 0, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 480:
			w, h = resize(480, 0, item.width, item.height)
			fmt.Printf("High   %d x %d\n", w, h)
			w, h = resize(360, 0, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		case input > 360:
			w, h = resize(360, 0, item.width, item.height)
			fmt.Printf("Normal %d x %d\n", w, h)
		}
		fmt.Printf("\n")
	}
}

/* exmaple 16:9
Org    3840 x 2160
High   1920 x 1080
Normal 854 x 480

Org    2560 x 1440
High   1920 x 1080
Normal 854 x 480

Org    1920 x 1080
High   1280 x 720
Normal 854 x 480

Org    1280 x 720
High   854 x 480
Normal 640 x 360

Org    960 x 540
High   854 x 480
Normal 640 x 360

Org    854 x 480
Normal 640 x 360

Org    640 x 360

Org    512 x 288

========================
Org    2160 x 3840
High   1080 x 1920
Normal 480 x 854

Org    1440 x 2560
High   1080 x 1920
Normal 480 x 854

Org    1080 x 1920
High   720 x 1280
Normal 480 x 854

Org    720 x 1280
High   480 x 854
Normal 360 x 640

Org    540 x 960
High   480 x 854
Normal 360 x 640

Org    480 x 854
Normal 360 x 640

Org    360 x 640

Org    288 x 512
*/

/* example 4:3
Org    2048 x 1536
High   1440 x 1080
Normal 640 x 480

Org    1600 x 1200
High   1440 x 1080
Normal 640 x 480

Org    1280 x 960
High   960 x 720
Normal 640 x 480

Org    800 x 600
High   640 x 480
Normal 480 x 360

Org    640 x 480
Normal 480 x 360

Org    512 x 384
Normal 480 x 360

Org    400 x 300

Org    320 x 240

========================
Org    1536 x 2048
High   1080 x 1440
Normal 480 x 640

Org    1200 x 1600
High   1080 x 1440
Normal 480 x 640

Org    960 x 1280
High   720 x 960
Normal 480 x 640

Org    600 x 800
High   480 x 640
Normal 360 x 480

Org    480 x 640
Normal 360 x 480

Org    384 x 512
Normal 360 x 480

Org    300 x 400

Org    240 x 320
*/

	Org	High	Normal
16:9 Horizontal
	3840 x 2160	1920 x 1080	854 x 480
	2560 x 1440	1920 x 1080	854 x 480
	1920 x 1080	1280 x 720	854 x 480
	1280 x 720	854 x 480	640 x 360
	960 x 540	854 x 480	640 x 360
	854 x 480		640 x 360
	640 x 360
	512 x 288
16:9 portrait	2160 x 3840	1080 x 1920	480 x 854
	1440 x 2560	1080 x 1920	480 x 854
	1080 x 1920	720 x 1280	480 x 854
	720 x 1280	480 x 854	360 x 640
	540 x 960	480 x 854	360 x 640
	480 x 854		360 x 640
	360 x 640
	288 x 512
4:3 Horizontal
	2048 x 1536	1440 x 1080	640 x 480
	1600 x 1200	1440 x 1080	640 x 480
	1280 x 960	960 x 720	640 x 480
	800 x 600	640 x 480	480 x 360
	640 x 480		480 x 360
	512 x 384		480 x 360
	400 x 300
	320 x 240
4:3 portrait
	1536 x 2048	1080 x 1440	480 x 640
	1200 x 1600	1080 x 1440	480 x 640
	960 x 1280	720 x 960	480 x 640
	600 x 800	480 x 640	360 x 480
	480 x 640		360 x 480
	384 x 512		360 x 480
	300 x 400
	240 x 320