main.go

package main

import (
	"image"
	"image/color"
	"image/draw"
	"image/jpeg"
	"log"
	"os"

	"github.com/disintegration/imaging"
	"github.com/golang/freetype/truetype"
	"golang.org/x/image/font"
	"golang.org/x/image/font/gofont/goregular"
	"golang.org/x/image/math/fixed"
)

func main() {
	// Open the background image to add the watermark
	img, err := imaging.Open("./assets/sample-1.jpeg")
	if err != nil {
		log.Fatalf("Failed to open: %s", err)
	}

	// image size
	imgSize := img.Bounds().Size()

	// create a string watermark with a name
	watermark := createWatermark("Govind Kailas", imgSize.X, imgSize.Y)

	// Add the overlay to the background image with 50% opacity
	result := imaging.Overlay(img, watermark, image.Point{0, 0}, 0.5)

	// Save the result image to file
	thirdImage, err := os.Create("image-with-overlay.jpg")
	if err != nil {
		log.Fatalf("Failed to create: %s", err)
	}
	jpeg.Encode(thirdImage, result, &jpeg.Options{Quality: 100})
	defer thirdImage.Close()
}

func createWatermark(name string, bgWidth, bgHeight int) *image.RGBA {
	// Create a new RGBA image
	img := image.NewRGBA(image.Rect(0, 0, bgWidth, bgHeight))

	// Load the font and create a font face
	fnt, err := truetype.Parse(goregular.TTF)
	if err != nil {
		panic(err)
	}

	// Create a font face with a proportional font size
	face := truetype.NewFace(fnt, &truetype.Options{
		Size: float64(bgWidth / 10),
	})

	// Calculate the width of the text using the font face
	width := font.MeasureString(face, name).Round()

	// Calculate the starting point of the text to center it
	// This will render from right to left
	startX := (img.Bounds().Dx() / 2) - width/2

	// this will render from bottom to top
	startY := (bgHeight / 2) + width/14

	// Draw the text onto the image
	col := color.RGBA{0, 0, 0, 128}
	draw.Draw(img, img.Bounds(), image.NewUniform(col), image.Point{}, draw.Src)

	watermark := &font.Drawer{
		Dst:  img,
		Src:  image.NewUniform(color.White),
		Face: face,
		Dot:  fixed.P(startX, startY),
	}

	// text shadow
	shadow := &font.Drawer{
		Dst:  img,
		Src:  image.NewUniform(color.Black),
		Face: face,
		Dot:  fixed.P(startX+2, startY+2),
	}

	shadow.DrawString(name)
	watermark.DrawString(name)

	return img
}