package utils

import (
	"bytes"
	"fmt"
	"github.com/disintegration/imaging"
	"image"
)

// AddWatermarkToImage 添加图片水印
func AddWatermarkToImage(fileBytes []byte, watermarkPath string) ([]byte, error) {
	// 将字节切片转为io.Reader
	reader := bytes.NewReader(fileBytes)

	// 从字节流中解码图片
	srcImage, err := imaging.Decode(reader)
	if err != nil {
		return nil, fmt.Errorf("图片解码失败: %w", err)
	}

	// 打开水印图片
	watermarkImage, err := imaging.Open(watermarkPath)
	if err != nil {
		return nil, fmt.Errorf("水印图片加载失败: %w", err)
	}

	// 获取原图片的宽高，用于水印的位置计算
	srcBounds := srcImage.Bounds()
	watermarkBounds := watermarkImage.Bounds()

	// 将水印添加到原图片的右下角
	offset := image.Pt(srcBounds.Max.X-watermarkBounds.Max.X, srcBounds.Max.Y-watermarkBounds.Max.Y)
	dstImage := imaging.Overlay(srcImage, watermarkImage, offset, 1.0)

	// 将处理后的图片保存到字节切片中
	var outputBuffer bytes.Buffer
	err = imaging.Encode(&outputBuffer, dstImage, imaging.PNG)
	if err != nil {
		return nil, fmt.Errorf("图片编码失败: %w", err)
	}

	return outputBuffer.Bytes(), nil
}