106 lines
2.6 KiB
Go
106 lines
2.6 KiB
Go
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package resize
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import (
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"bytes"
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"github.com/anthonynsimon/bild/transform"
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"image"
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"image/jpeg"
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"image/png"
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"io"
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)
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var mimeTypes = map[string]string{
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"image/jpg": "image/jpg",
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"image/jpeg": "image/jpeg",
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"image/png": "image/png",
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}
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func IsResizable(mimeType string) bool {
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_, present := mimeTypes[mimeType]
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return present
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}
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type ResizeType int
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const (
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// Cover - resize preserving image aspect
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// - resizes to the smallest image where both width and height are larger or equal to given size
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Cover ResizeType = iota
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// Contain - resize preserving image aspect
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// - resizes to the largest image where both width and height are smaller or equal to given size
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Contain ResizeType = iota
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// ExactHeight - resize preserving image aspect
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// - resizes to the image with given height
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ExactHeight ResizeType = iota
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// ExactWidth - resize preserving image aspect
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// - resizes to the image with given width
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ExactWidth ResizeType = iota
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// Exact - resize without preserving image aspect
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// - resizes to exact size defined in request
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Exact ResizeType = iota
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)
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type Resize struct {
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Height int
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Width int
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Type ResizeType
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}
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func ResizeImage(imageBytes []byte, resize Resize) ([]byte, error) {
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img, format, err := image.Decode(bytes.NewReader(imageBytes))
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if err != nil {
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return nil, err
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}
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var buffer bytes.Buffer
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writer := io.Writer(&buffer)
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resizeWidth, resizeHeight := calculateResizedDimensions(img.Bounds(), resize)
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img = transform.Resize(img, resizeWidth, resizeHeight, transform.Gaussian)
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switch format {
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case "png":
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err = png.Encode(writer, img)
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case "jpeg":
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err = jpeg.Encode(writer, img, nil)
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default:
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err = jpeg.Encode(writer, img, nil)
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}
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if err != nil {
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return nil, err
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}
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return buffer.Bytes(), nil
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}
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func calculateResizedDimensions(bounds image.Rectangle, resize Resize) (width int, height int) {
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width = bounds.Dx()
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height = bounds.Dy()
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switch resize.Type {
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case Cover:
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rWidth := resize.Height * width / height
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if rWidth >= resize.Width {
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return rWidth, resize.Height
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}
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rHeight := resize.Width * height / width
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if rHeight >= resize.Height {
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return resize.Width, rHeight
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}
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case Contain:
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rWidth := resize.Height * width / height
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if rWidth <= resize.Width {
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return rWidth, resize.Height
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}
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rHeight := resize.Width * height / width
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if rHeight <= resize.Height {
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return resize.Width, rHeight
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}
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case ExactHeight:
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rWidth := resize.Height * width / height
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return rWidth, resize.Height
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case ExactWidth:
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rHeight := resize.Width * height / width
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return resize.Width, rHeight
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}
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return
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}
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