135 lines
3.2 KiB
Go
135 lines
3.2 KiB
Go
package images
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import (
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"bytes"
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"encoding/base64"
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"errors"
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"fmt"
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"image"
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"image/jpeg"
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"io"
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"regexp"
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"strings"
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"github.com/nfnt/resize"
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)
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type EncodeConfig struct {
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Quality int
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}
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func Encode(w io.Writer, img image.Image, config EncodeConfig) error {
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// Currently a wrapper for renderJpeg, but this function is useful if multiple render formats are needed
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return renderJpeg(w, img, config)
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}
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func renderJpeg(w io.Writer, m image.Image, config EncodeConfig) error {
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o := new(jpeg.Options)
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o.Quality = config.Quality
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return jpeg.Encode(w, m, o)
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}
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type FileSizeError struct {
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expected int
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received int
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}
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func (e *FileSizeError) Error() string {
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return fmt.Sprintf("image size after processing exceeds max, expected < '%d', received < '%d'", e.expected, e.received)
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}
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func EncodeToLimits(bb *bytes.Buffer, img image.Image, bounds FileSizeLimits) error {
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q := MaxJpegQuality
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for q > MinJpegQuality-1 {
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err := Encode(bb, img, EncodeConfig{Quality: q})
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if err != nil {
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return err
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}
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if bounds.Ideal > bb.Len() {
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return nil
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}
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if q == MinJpegQuality {
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if bounds.Max > bb.Len() {
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return nil
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}
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return &FileSizeError{expected: bounds.Max, received: bb.Len()}
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}
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bb.Reset()
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q -= 2
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}
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return nil
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}
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// CompressToFileLimits takes an image.Image and analyses the pixel dimensions, if the longest side is greater
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// than the `longSideMax` image.Image will be resized, before compression begins.
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// Next the image.Image is repeatedly encoded and resized until the data fits within
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// the given FileSizeLimits. There is no limit on the number of times the cycle is performed, the image.Image
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// is reduced to 95% of its size at the end of every round the file size exceeds the given limits.
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func CompressToFileLimits(bb *bytes.Buffer, img image.Image, bounds FileSizeLimits) error {
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longSideMax := 2000
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// Do we need to do a pre-compression resize?
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if img.Bounds().Max.X > img.Bounds().Max.Y {
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// X is longer
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if img.Bounds().Max.X > longSideMax {
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img = resize.Resize(uint(longSideMax), 0, img, resize.Bilinear)
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}
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} else {
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// Y is longer or equal
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if img.Bounds().Max.Y > longSideMax {
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img = resize.Resize(0, uint(longSideMax), img, resize.Bilinear)
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}
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}
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for {
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err := EncodeToLimits(bb, img, bounds)
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if err == nil {
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return nil
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}
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// If error is not a FileSizeError then we need to return it up
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if fse := (*FileSizeError)(nil); !errors.As(err, &fse) {
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return err
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}
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img = ResizeTo(95, img)
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}
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}
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func EncodeToBestSize(bb *bytes.Buffer, img image.Image, size ResizeDimension) error {
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return EncodeToLimits(bb, img, DimensionSizeLimit[size])
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}
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func GetPayloadDataURI(payload []byte) (string, error) {
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if len(payload) == 0 {
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return "", nil
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}
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mt, err := GetMimeType(payload)
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if err != nil {
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return "", err
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}
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b64 := base64.StdEncoding.EncodeToString(payload)
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return "data:image/" + mt + ";base64," + b64, nil
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}
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func GetPayloadFromURI(uri string) ([]byte, error) {
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re := regexp.MustCompile("^data:image/(.*?);base64,(.*?)$")
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res := re.FindStringSubmatch(uri)
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if len(res) != 3 {
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return nil, errors.New("wrong uri format")
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}
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return base64.StdEncoding.DecodeString(res[2])
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}
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func IsPayloadDataURI(uri string) bool {
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return strings.HasPrefix(uri, "data:image")
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}
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