46 lines
1.1 KiB
Go
46 lines
1.1 KiB
Go
package vision
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import (
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"bytes"
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"fmt"
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"image"
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"image/jpeg"
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"golang.org/x/image/draw"
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)
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// EncodeJPEG 把图像等比缩放到长边不超过 maxEdge 后编码为 JPEG。
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// 视觉模型对分辨率不敏感，但对 token 很敏感，这一步是成本控制的关键。
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func EncodeJPEG(img image.Image, maxEdge, quality int) ([]byte, error) {
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if img == nil {
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return nil, fmt.Errorf("待编码图像为空")
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}
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if maxEdge <= 0 {
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maxEdge = 1280
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}
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if quality <= 0 || quality > 100 {
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quality = 75
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}
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b := img.Bounds()
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w, h := b.Dx(), b.Dy()
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if w <= 0 || h <= 0 {
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return nil, fmt.Errorf("图像尺寸无效: %dx%d", w, h)
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}
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target := img
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if longest := max(w, h); longest > maxEdge {
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scale := float64(maxEdge) / float64(longest)
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nw, nh := max(int(float64(w)*scale+0.5), 1), max(int(float64(h)*scale+0.5), 1)
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dst := image.NewRGBA(image.Rect(0, 0, nw, nh))
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draw.CatmullRom.Scale(dst, dst.Bounds(), img, b, draw.Src, nil)
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target = dst
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}
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var buf bytes.Buffer
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if err := jpeg.Encode(&buf, target, &jpeg.Options{Quality: quality}); err != nil {
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return nil, fmt.Errorf("JPEG 编码失败: %w", err)
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}
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return buf.Bytes(), nil
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}
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