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39 lines
811 B
39 lines
811 B
package png
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import (
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"bytes"
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"github.com/foobaz/lossypng/lossypng"
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"image"
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"image/png"
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"io"
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)
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const qMax = 20
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// Options represent PNG encoding options.
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type Options struct {
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Quality int `json:"quality"`
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}
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// DecodePNG decodes a PNG file and return an image.
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func DecodePNG(r io.Reader) (image.Image, error) {
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i, err := png.Decode(r)
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if err != nil {
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return nil, err
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}
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return i, nil
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}
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// EncodePNG encodes an image into PNG and returns a buffer.
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func EncodePNG(i image.Image, o *Options) (buf bytes.Buffer, err error) {
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c := lossypng.Compress(i, 2, qualityFactor(o.Quality))
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err = png.Encode(&buf, c)
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return buf, err
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}
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// qualityFactor normalizes the PNG quality factor from a max of 20, where 0 is
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// no conversion.
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func qualityFactor(q int) int {
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f := q / 100
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return qMax - (f * qMax)
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}
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