webp

models/Image.go

@@ -1,10 +1,18 @@
 package models
 
 import (
+	"bytes"
 	"database/sql/driver"
 	"encoding/json"
+	"fmt"
+	"image"
+	"io/ioutil"
 	"main/configs"
 	"time"
+
+	"github.com/chai2010/webp"
+	"github.com/disintegration/imaging"
+	giftowebp "github.com/sizeofint/gif-to-webp"
 )
 
 type Image struct {
@@ -24,6 +32,56 @@ type Image struct {
 	UpdatedAt         time.Time `json:"updated_at" gorm:"autoUpdateTime"`
 }
 
+// 将图片输出为指定尺寸的 webp 格式(默认使用 Lanczos 缩放算法)
+func (img *Image) ToWebP(width int, height int, fit string) ([]byte, error) {
+	// 從絕對路徑讀原始圖片
+	data, err := ioutil.ReadFile(fmt.Sprintf("data/images/%d", img.ID))
+	if err != nil {
+		return nil, err
+	}
+	// 將原始圖片轉換為 Image
+	imageData, format, err := image.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+
+	// 如果原图是GIF格式的动态图片，直接不作尺寸处理，直接转换为webp格式
+	if format == "gif" {
+		converter := giftowebp.NewConverter()
+		converter.LoopCompatibility = true   // 是否兼容循环动画
+		converter.WebPConfig.SetLossless(1)  // 0 有损压缩 1无损压缩
+		converter.WebPConfig.SetMethod(6)    // 压缩速度 0-6 0最快 6质量最好
+		converter.WebPConfig.SetQuality(100) // 压缩质量 0-100
+		converter.WebPAnimEncoderOptions.SetKmin(9)
+		converter.WebPAnimEncoderOptions.SetKmax(17)
+		return converter.Convert(data)
+	}
+	// 如果指定了宽高却没有指定fit, 则默认fit为cover
+	if width != 0 && height != 0 && fit == "" {
+		fit = "cover"
+	}
+	// 如果未指定宽高和fit, 则不缩放图片直接返回webp
+	if width == 0 && height == 0 && fit == "" {
+		return webp.EncodeRGBA(imageData, 100)
+	}
+	switch fit {
+	case "cover":
+		return webp.EncodeRGBA(imaging.Fill(imageData, width, height, imaging.Center, imaging.Lanczos), 100)
+	case "contain":
+		return webp.EncodeRGBA(imaging.Fit(imageData, width, height, imaging.Lanczos), 100)
+	case "fill":
+		return webp.EncodeRGBA(imaging.Fill(imageData, width, height, imaging.Center, imaging.Lanczos), 100)
+	case "inside":
+		return webp.EncodeRGBA(imaging.Fit(imageData, width, height, imaging.Lanczos), 100)
+	case "outside":
+		return webp.EncodeRGBA(imaging.Fill(imageData, width, height, imaging.Center, imaging.Lanczos), 100)
+	case "scale-down":
+		return webp.EncodeRGBA(imaging.Fit(imageData, width, height, imaging.Lanczos), 100)
+	default:
+		return webp.EncodeRGBA(imaging.Resize(imageData, width, height, imaging.Lanczos), 100)
+	}
+}
+
 func init() {
 	configs.ORMDB().AutoMigrate(&Image{})
 }