Add MediaConvertWebPToPNG option (telegram). (#741)

* Add MediaConvertWebPToPNG option (telegram).

When enabled matterbridge will convert .webp files to .png files
before uploading them to the mediaserver of the other bridges.

Fixes #398

2 files changed, 279 insertions, 0 deletions

diff --git a/vendor/golang.org/x/image/webp/decode.go b/vendor/golang.org/x/image/webp/decode.go
new file mode 100644
index 00000000..f77a4ebf
--- /dev/null
+++ b/vendor/golang.org/x/image/webp/decode.go
@@ -0,0 +1,270 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package webp
+
+import (
+	"bytes"
+	"errors"
+	"image"
+	"image/color"
+	"io"
+
+	"golang.org/x/image/riff"
+	"golang.org/x/image/vp8"
+	"golang.org/x/image/vp8l"
+)
+
+var errInvalidFormat = errors.New("webp: invalid format")
+
+var (
+	fccALPH = riff.FourCC{'A', 'L', 'P', 'H'}
+	fccVP8  = riff.FourCC{'V', 'P', '8', ' '}
+	fccVP8L = riff.FourCC{'V', 'P', '8', 'L'}
+	fccVP8X = riff.FourCC{'V', 'P', '8', 'X'}
+	fccWEBP = riff.FourCC{'W', 'E', 'B', 'P'}
+)
+
+func decode(r io.Reader, configOnly bool) (image.Image, image.Config, error) {
+	formType, riffReader, err := riff.NewReader(r)
+	if err != nil {
+		return nil, image.Config{}, err
+	}
+	if formType != fccWEBP {
+		return nil, image.Config{}, errInvalidFormat
+	}
+
+	var (
+		alpha          []byte
+		alphaStride    int
+		wantAlpha      bool
+		widthMinusOne  uint32
+		heightMinusOne uint32
+		buf            [10]byte
+	)
+	for {
+		chunkID, chunkLen, chunkData, err := riffReader.Next()
+		if err == io.EOF {
+			err = errInvalidFormat
+		}
+		if err != nil {
+			return nil, image.Config{}, err
+		}
+
+		switch chunkID {
+		case fccALPH:
+			if !wantAlpha {
+				return nil, image.Config{}, errInvalidFormat
+			}
+			wantAlpha = false
+			// Read the Pre-processing | Filter | Compression byte.
+			if _, err := io.ReadFull(chunkData, buf[:1]); err != nil {
+				if err == io.EOF {
+					err = errInvalidFormat
+				}
+				return nil, image.Config{}, err
+			}
+			alpha, alphaStride, err = readAlpha(chunkData, widthMinusOne, heightMinusOne, buf[0]&0x03)
+			if err != nil {
+				return nil, image.Config{}, err
+			}
+			unfilterAlpha(alpha, alphaStride, (buf[0]>>2)&0x03)
+
+		case fccVP8:
+			if wantAlpha || int32(chunkLen) < 0 {
+				return nil, image.Config{}, errInvalidFormat
+			}
+			d := vp8.NewDecoder()
+			d.Init(chunkData, int(chunkLen))
+			fh, err := d.DecodeFrameHeader()
+			if err != nil {
+				return nil, image.Config{}, err
+			}
+			if configOnly {
+				return nil, image.Config{
+					ColorModel: color.YCbCrModel,
+					Width:      fh.Width,
+					Height:     fh.Height,
+				}, nil
+			}
+			m, err := d.DecodeFrame()
+			if err != nil {
+				return nil, image.Config{}, err
+			}
+			if alpha != nil {
+				return &image.NYCbCrA{
+					YCbCr:   *m,
+					A:       alpha,
+					AStride: alphaStride,
+				}, image.Config{}, nil
+			}
+			return m, image.Config{}, nil
+
+		case fccVP8L:
+			if wantAlpha || alpha != nil {
+				return nil, image.Config{}, errInvalidFormat
+			}
+			if configOnly {
+				c, err := vp8l.DecodeConfig(chunkData)
+				return nil, c, err
+			}
+			m, err := vp8l.Decode(chunkData)
+			return m, image.Config{}, err
+
+		case fccVP8X:
+			if chunkLen != 10 {
+				return nil, image.Config{}, errInvalidFormat
+			}
+			if _, err := io.ReadFull(chunkData, buf[:10]); err != nil {
+				return nil, image.Config{}, err
+			}
+			const (
+				animationBit    = 1 << 1
+				xmpMetadataBit  = 1 << 2
+				exifMetadataBit = 1 << 3
+				alphaBit        = 1 << 4
+				iccProfileBit   = 1 << 5
+			)
+			if buf[0] != alphaBit {
+				return nil, image.Config{}, errors.New("webp: non-Alpha VP8X is not implemented")
+			}
+			widthMinusOne = uint32(buf[4]) | uint32(buf[5])<<8 | uint32(buf[6])<<16
+			heightMinusOne = uint32(buf[7]) | uint32(buf[8])<<8 | uint32(buf[9])<<16
+			if configOnly {
+				return nil, image.Config{
+					ColorModel: color.NYCbCrAModel,
+					Width:      int(widthMinusOne) + 1,
+					Height:     int(heightMinusOne) + 1,
+				}, nil
+			}
+			wantAlpha = true
+
+		default:
+			return nil, image.Config{}, errInvalidFormat
+		}
+	}
+}
+
+func readAlpha(chunkData io.Reader, widthMinusOne, heightMinusOne uint32, compression byte) (
+	alpha []byte, alphaStride int, err error) {
+
+	switch compression {
+	case 0:
+		w := int(widthMinusOne) + 1
+		h := int(heightMinusOne) + 1
+		alpha = make([]byte, w*h)
+		if _, err := io.ReadFull(chunkData, alpha); err != nil {
+			return nil, 0, err
+		}
+		return alpha, w, nil
+
+	case 1:
+		// Read the VP8L-compressed alpha values. First, synthesize a 5-byte VP8L header:
+		// a 1-byte magic number, a 14-bit widthMinusOne, a 14-bit heightMinusOne,
+		// a 1-bit (ignored, zero) alphaIsUsed and a 3-bit (zero) version.
+		// TODO(nigeltao): be more efficient than decoding an *image.NRGBA just to
+		// extract the green values to a separately allocated []byte. Fixing this
+		// will require changes to the vp8l package's API.
+		if widthMinusOne > 0x3fff || heightMinusOne > 0x3fff {
+			return nil, 0, errors.New("webp: invalid format")
+		}
+		alphaImage, err := vp8l.Decode(io.MultiReader(
+			bytes.NewReader([]byte{
+				0x2f, // VP8L magic number.
+				uint8(widthMinusOne),
+				uint8(widthMinusOne>>8) | uint8(heightMinusOne<<6),
+				uint8(heightMinusOne >> 2),
+				uint8(heightMinusOne >> 10),
+			}),
+			chunkData,
+		))
+		if err != nil {
+			return nil, 0, err
+		}
+		// The green values of the inner NRGBA image are the alpha values of the
+		// outer NYCbCrA image.
+		pix := alphaImage.(*image.NRGBA).Pix
+		alpha = make([]byte, len(pix)/4)
+		for i := range alpha {
+			alpha[i] = pix[4*i+1]
+		}
+		return alpha, int(widthMinusOne) + 1, nil
+	}
+	return nil, 0, errInvalidFormat
+}
+
+func unfilterAlpha(alpha []byte, alphaStride int, filter byte) {
+	if len(alpha) == 0 || alphaStride == 0 {
+		return
+	}
+	switch filter {
+	case 1: // Horizontal filter.
+		for i := 1; i < alphaStride; i++ {
+			alpha[i] += alpha[i-1]
+		}
+		for i := alphaStride; i < len(alpha); i += alphaStride {
+			// The first column is equivalent to the vertical filter.
+			alpha[i] += alpha[i-alphaStride]
+
+			for j := 1; j < alphaStride; j++ {
+				alpha[i+j] += alpha[i+j-1]
+			}
+		}
+
+	case 2: // Vertical filter.
+		// The first row is equivalent to the horizontal filter.
+		for i := 1; i < alphaStride; i++ {
+			alpha[i] += alpha[i-1]
+		}
+
+		for i := alphaStride; i < len(alpha); i++ {
+			alpha[i] += alpha[i-alphaStride]
+		}
+
+	case 3: // Gradient filter.
+		// The first row is equivalent to the horizontal filter.
+		for i := 1; i < alphaStride; i++ {
+			alpha[i] += alpha[i-1]
+		}
+
+		for i := alphaStride; i < len(alpha); i += alphaStride {
+			// The first column is equivalent to the vertical filter.
+			alpha[i] += alpha[i-alphaStride]
+
+			// The interior is predicted on the three top/left pixels.
+			for j := 1; j < alphaStride; j++ {
+				c := int(alpha[i+j-alphaStride-1])
+				b := int(alpha[i+j-alphaStride])
+				a := int(alpha[i+j-1])
+				x := a + b - c
+				if x < 0 {
+					x = 0
+				} else if x > 255 {
+					x = 255
+				}
+				alpha[i+j] += uint8(x)
+			}
+		}
+	}
+}
+
+// Decode reads a WEBP image from r and returns it as an image.Image.
+func Decode(r io.Reader) (image.Image, error) {
+	m, _, err := decode(r, false)
+	if err != nil {
+		return nil, err
+	}
+	return m, err
+}
+
+// DecodeConfig returns the color model and dimensions of a WEBP image without
+// decoding the entire image.
+func DecodeConfig(r io.Reader) (image.Config, error) {
+	_, c, err := decode(r, true)
+	return c, err
+}
+
+func init() {
+	image.RegisterFormat("webp", "RIFF????WEBPVP8", Decode, DecodeConfig)
+}
diff --git a/vendor/golang.org/x/image/webp/doc.go b/vendor/golang.org/x/image/webp/doc.go
new file mode 100644
index 00000000..e321c854
--- /dev/null
+++ b/vendor/golang.org/x/image/webp/doc.go
@@ -0,0 +1,9 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package webp implements a decoder for WEBP images.
+//
+// WEBP is defined at:
+// https://developers.google.com/speed/webp/docs/riff_container
+package webp // import "golang.org/x/image/webp"