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package media
import (
"bytes"
"encoding/base64"
"fmt"
"image/png"
"github.com/davidbyttow/govips/v2/vips"
thumbhash "go.n16f.net/thumbhash"
)
// ImageInfo returns the pixel dimensions and a base64-encoded thumbhash for
// the image at path. The thumbhash is generated from a ≤100px thumbnail so
// it is fast regardless of the original size.
func ImageInfo(path string) (width, height int, thumbhashB64 string, err error) {
img, err := vips.NewImageFromFile(path)
if err != nil {
return 0, 0, "", fmt.Errorf("load %s: %w", path, err)
}
defer img.Close()
width = img.Width()
height = img.Height()
const maxThumbDim = 100
if width > maxThumbDim || height > maxThumbDim {
scale := float64(maxThumbDim) / float64(max(width, height))
if err := img.Resize(scale, vips.KernelLanczos3); err != nil {
return width, height, "", fmt.Errorf("resize for thumbhash: %w", err)
}
}
pngBytes, _, err := img.ExportPng(vips.NewPngExportParams())
if err != nil {
return width, height, "", fmt.Errorf("export png for thumbhash: %w", err)
}
goImg, err := png.Decode(bytes.NewReader(pngBytes))
if err != nil {
return width, height, "", fmt.Errorf("decode png for thumbhash: %w", err)
}
hash := thumbhash.EncodeImage(goImg)
return width, height, base64.StdEncoding.EncodeToString(hash), nil
}
// ConvertAndResize loads the image at src, optionally resizes it to width pixels
// wide (maintaining aspect ratio), and exports it in the requested format.
//
// width <= 0 means no resize. format must be "webp" or "jpeg".
func ConvertAndResize(src string, width int, format string) ([]byte, error) {
img, err := vips.NewImageFromFile(src)
if err != nil {
return nil, fmt.Errorf("load image %s: %w", src, err)
}
defer img.Close()
if width > 0 && width < img.Width() {
scale := float64(width) / float64(img.Width())
if err := img.Resize(scale, vips.KernelLanczos3); err != nil {
return nil, fmt.Errorf("resize: %w", err)
}
}
switch format {
case "webp":
buf, _, err := img.ExportWebp(vips.NewWebpExportParams())
if err != nil {
return nil, fmt.Errorf("export webp: %w", err)
}
return buf, nil
case "jpeg":
buf, _, err := img.ExportJpeg(vips.NewJpegExportParams())
if err != nil {
return nil, fmt.Errorf("export jpeg: %w", err)
}
return buf, nil
default:
return nil, fmt.Errorf("unsupported format %q: must be webp or jpeg", format)
}
}
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