88 lines
2.2 KiB
Go
88 lines
2.2 KiB
Go
package main
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import (
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"context"
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"fmt"
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"image"
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"image/color"
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"image/draw"
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_ "image/gif"
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"image/jpeg"
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_ "image/png"
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"io"
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"net/http"
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"os"
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"path/filepath"
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"time"
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_ "golang.org/x/image/webp"
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)
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const maxImageBytes = 50 << 20
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type Downloader struct {
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client *http.Client
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}
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func newDownloader() *Downloader {
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return &Downloader{client: &http.Client{Timeout: 45 * time.Second}}
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}
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func (d *Downloader) download(ctx context.Context, apiURL, destination string) error {
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req, err := http.NewRequestWithContext(ctx, http.MethodGet, apiURL, nil)
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if err != nil {
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return fmt.Errorf("创建图片请求: %w", err)
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}
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req.Header.Set("User-Agent", "GoWallpaper/1.0")
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req.Header.Set("Accept", "image/*")
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resp, err := d.client.Do(req)
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if err != nil {
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return fmt.Errorf("请求图片 API: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode < 200 || resp.StatusCode >= 300 {
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return fmt.Errorf("图片 API 返回 HTTP %d", resp.StatusCode)
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}
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if resp.ContentLength > maxImageBytes {
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return fmt.Errorf("图片超过 %d MB 限制", maxImageBytes>>20)
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}
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limited := io.LimitReader(resp.Body, maxImageBytes+1)
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img, _, err := image.Decode(limited)
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if err != nil {
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return fmt.Errorf("API 响应不是支持的图片: %w", err)
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}
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if img.Bounds().Dx() <= 0 || img.Bounds().Dy() <= 0 {
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return fmt.Errorf("API 返回了无效尺寸的图片")
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}
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// JPEG 没有透明通道，先铺黑色背景可避免透明图片出现不可预测颜色。
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bounds := img.Bounds()
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flat := image.NewRGBA(image.Rect(0, 0, bounds.Dx(), bounds.Dy()))
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draw.Draw(flat, flat.Bounds(), &image.Uniform{C: color.Black}, image.Point{}, draw.Src)
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draw.Draw(flat, flat.Bounds(), img, bounds.Min, draw.Over)
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tmp, err := os.CreateTemp(filepath.Dir(destination), ".download-*.jpg")
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if err != nil {
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return fmt.Errorf("创建缓存文件: %w", err)
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}
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tmpName := tmp.Name()
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defer os.Remove(tmpName)
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if err := jpeg.Encode(tmp, flat, &jpeg.Options{Quality: 92}); err != nil {
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tmp.Close()
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return fmt.Errorf("保存图片: %w", err)
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}
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if err := tmp.Sync(); err != nil {
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tmp.Close()
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return err
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}
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if err := tmp.Close(); err != nil {
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return err
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}
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if err := os.Rename(tmpName, destination); err != nil {
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return fmt.Errorf("保存缓存图片: %w", err)
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}
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return nil
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}
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