Image manipulation library for web written in Go. https://fedi.dev/webimg/
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/*
* Copyright © 2020 Gytis Repečka (gytis@repecka.com)
*
* This file is part of webimg.
*
* webimg is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, included
* in the LICENSE file in this source code package.
*/
package webimg
import (
"fmt"
"image"
"image/color"
"image/draw"
"image/jpeg"
"image/png"
"log"
"os"
)
func PrintHello() {
fmt.Println("Hello there!")
}
func Watermark(imagePath, watermarkPath, resultPath string, offsetX, offsetY int, watermarkAlpha uint8) (err error) {
// Input image
// To-do: need to sanitize image paths!
image1, err := os.Open(imagePath)
if err != nil {
log.Fatalf("failed to open: %s", err)
}
first, err := jpeg.Decode(image1)
if err != nil {
log.Fatalf("failed to decode: %s", err)
}
defer image1.Close()
// Watermark image
image2, err := os.Open(watermarkPath)
if err != nil {
log.Fatalf("failed to open: %s", err)
}
second, err := png.Decode(image2)
if err != nil {
log.Fatalf("failed to decode: %s", err)
}
defer image2.Close()
// x, y from top-left corner
// offset := image.Pt(100, 50)
// log.Printf("Point: %V (%T)\n", offset, offset)
// Bounds of input image
inBounds := first.Bounds()
// Bounds of watermark image
watermarkBounds := second.Bounds()
// To-do: offset should be configurable!
watermarkCoordX1 := inBounds.Max.X - offsetX - watermarkBounds.Max.X // Input image x2 - offset x - watermark x2
watermarkCoordY1 := inBounds.Max.Y - offsetY - watermarkBounds.Max.Y // Input image y2 - offset y - watermark y2
offset := image.Pt(watermarkCoordX1, watermarkCoordY1)
outBoundsOff := watermarkBounds.Add(offset)
// outBoundsOff := inBounds.Sub(offset)
/*
log.Printf("Bounds (input): %V (%T)\n", inBounds, inBounds)
log.Printf("Bounds (watermark): %V (%T)\n", watermarkBounds, watermarkBounds)
log.Printf("Bounds (watermark with offset): %V (%T)\n", outBoundsOff, outBoundsOff)
*/
log.Printf("Watermark x1: %d, y1: %d, x2: %d, y2: %d.", outBoundsOff.Min.X, outBoundsOff.Min.Y, outBoundsOff.Max.X, outBoundsOff.Max.Y)
// Create new (output) image with size (bounds) of input image
image3 := image.NewRGBA(inBounds)
// Transparency
// 0 - 255
mask := image.NewUniform(color.Alpha{watermarkAlpha})
draw.Draw(image3, inBounds, first, image.ZP, draw.Src)
draw.DrawMask(image3, outBoundsOff, second, image.ZP, mask, image.ZP, draw.Over)
third, err := os.Create(resultPath)
if err != nil {
log.Fatalf("failed to create: %s", err)
}
// jpeg.Encode(third, image3, &jpeg.Options{jpeg.DefaultQuality})
jpeg.Encode(third, image3, &jpeg.Options{85})
defer third.Close()
return err
}