Convert .tgs with go libraries (and cgo) (telegram) (#1569)

This commit adds support for go/cgo tgs conversion when building with the -tags `cgo`
The default binaries are still "pure" go and uses the old way of converting.

* Move lottie_convert.py conversion code to its own file

* Add optional libtgsconverter

* Update vendor

* Apply suggestions from code review

* Update bridge/helper/libtgsconverter.go

Co-authored-by: Wim <wim@42.be>

vendor/github.com/sizeofint/webpanimation/webpanimation.go

@@ -0,0 +1,109 @@
+package webpanimation
+
+import (
+	"errors"
+	"fmt"
+	"image"
+	"image/draw"
+	"io"
+)
+
+type WebpAnimation struct {
+	WebPAnimEncoderOptions *WebPAnimEncoderOptions
+	Width                  int
+	Height                 int
+	loopCount              int
+	AnimationEncoder       *WebPAnimEncoder
+	WebPData               *WebPData
+	WebPMux                *WebPMux
+	WebPPictures           []*WebPPicture
+}
+
+// NewWebpAnimation Initialize animation
+func NewWebpAnimation(width, height, loopCount int) *WebpAnimation {
+	webpAnimation := &WebpAnimation{loopCount: loopCount, Width: width, Height: height}
+	webpAnimation.WebPAnimEncoderOptions = &WebPAnimEncoderOptions{}
+
+	WebPAnimEncoderOptionsInitInternal(webpAnimation.WebPAnimEncoderOptions)
+
+	webpAnimation.AnimationEncoder = WebPAnimEncoderNewInternal(width, height, webpAnimation.WebPAnimEncoderOptions)
+	return webpAnimation
+}
+
+// ReleaseMemory release memory
+func (wpa *WebpAnimation) ReleaseMemory() {
+	WebPDataClear(wpa.WebPData)
+	WebPMuxDelete(wpa.WebPMux)
+	for _, webpPicture := range wpa.WebPPictures {
+		WebPPictureFree(webpPicture)
+	}
+	WebPAnimEncoderDelete(wpa.AnimationEncoder)
+}
+
+// AddFrame add frame to animation
+func (wpa *WebpAnimation) AddFrame(img image.Image, timestamp int, webpcfg WebPConfig) error {
+	var webPPicture *WebPPicture = nil
+	var m *image.RGBA
+	if img != nil {
+		if v, ok := img.(*image.RGBA); ok {
+			m = v
+		} else {
+			b := img.Bounds()
+			m = image.NewRGBA(image.Rect(0, 0, b.Dx(), b.Dy()))
+			draw.Draw(m, m.Bounds(), img, b.Min, draw.Src)
+		}
+
+		webPPicture = &WebPPicture{}
+		wpa.WebPPictures = append(wpa.WebPPictures, webPPicture)
+		webPPicture.SetUseArgb(1)
+		webPPicture.SetHeight(wpa.Height)
+		webPPicture.SetWidth(wpa.Width)
+		err := WebPPictureImportRGBA(m.Pix, m.Stride, webPPicture)
+		if err != nil {
+			return err
+		}
+	}
+
+	res := WebPAnimEncoderAdd(wpa.AnimationEncoder, webPPicture, timestamp, webpcfg)
+	if res == 0 {
+		return errors.New("Failed to add frame in animation ecoder")
+	}
+	return nil
+}
+
+// Encode encode animation
+func (wpa *WebpAnimation) Encode(w io.Writer) error {
+	wpa.WebPData = &WebPData{}
+
+	WebPDataInit(wpa.WebPData)
+
+	WebPAnimEncoderAssemble(wpa.AnimationEncoder, wpa.WebPData)
+
+	if wpa.loopCount > 0 {
+		wpa.WebPMux = WebPMuxCreateInternal(wpa.WebPData, 1)
+		if wpa.WebPMux == nil {
+			return errors.New("ERROR: Could not re-mux to add loop count/metadata.")
+		}
+		WebPDataClear(wpa.WebPData)
+
+		webPMuxAnimNewParams := WebPMuxAnimParams{}
+		muxErr := WebPMuxGetAnimationParams(wpa.WebPMux, &webPMuxAnimNewParams)
+		if muxErr != WebpMuxOk {
+			return errors.New("Could not fetch loop count")
+		}
+		webPMuxAnimNewParams.SetLoopCount(wpa.loopCount)
+
+		muxErr = WebPMuxSetAnimationParams(wpa.WebPMux, &webPMuxAnimNewParams)
+		if muxErr != WebpMuxOk {
+			return errors.New(fmt.Sprint("Could not update loop count, code:", muxErr))
+		}
+
+		muxErr = WebPMuxAssemble(wpa.WebPMux, wpa.WebPData)
+		if muxErr != WebpMuxOk {
+			return errors.New("Could not assemble when re-muxing to add")
+		}
+
+	}
+	_, err := w.Write(wpa.WebPData.GetBytes())
+	return err
+}