Exemple #1
0
        /// <summary>
        /// Reads the application extension block parsing any animation information
        /// if present.
        /// </summary>
        private void ReadApplicationExtension()
        {
            int appLength = this.stream.ReadByte();

            // If the length is 11 then it's a valid extension and most likely
            // a NETSCAPE or ANIMEXTS extension. We want the loop count from this.
            if (appLength == GifConstants.ApplicationBlockSize)
            {
                this.stream.Skip(appLength);
                int subBlockSize = this.stream.ReadByte();

                // TODO: There's also a NETSCAPE buffer extension.
                // http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
                if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
                {
                    this.stream.Read(this.buffer, 0, GifConstants.NetscapeLoopingSubBlockSize);
                    this.gifMetadata.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.AsSpan(1)).RepeatCount;
                    this.stream.Skip(1); // Skip the terminator.
                    return;
                }

                // Could be XMP or something else not supported yet.
                // Skip the subblock and terminator.
                this.SkipBlock(subBlockSize);
                return;
            }

            this.SkipBlock(appLength); // Not supported by any known decoder.
        }
        /// <summary>
        /// Reads the application extension block parsing any animation or XMP information
        /// if present.
        /// </summary>
        private void ReadApplicationExtension()
        {
            int appLength = this.stream.ReadByte();

            // If the length is 11 then it's a valid extension and most likely
            // a NETSCAPE, XMP or ANIMEXTS extension. We want the loop count from this.
            if (appLength == GifConstants.ApplicationBlockSize)
            {
                this.stream.Read(this.buffer, 0, GifConstants.ApplicationBlockSize);
                bool isXmp = this.buffer.AsSpan().StartsWith(GifConstants.XmpApplicationIdentificationBytes);

                if (isXmp && !this.IgnoreMetadata)
                {
                    var extension = GifXmpApplicationExtension.Read(this.stream, this.MemoryAllocator);
                    if (extension.Data.Length > 0)
                    {
                        this.metadata.XmpProfile = new XmpProfile(extension.Data);
                    }

                    return;
                }
                else
                {
                    int subBlockSize = this.stream.ReadByte();

                    // TODO: There's also a NETSCAPE buffer extension.
                    // http://www.vurdalakov.net/misc/gif/netscape-buffering-application-extension
                    if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
                    {
                        this.stream.Read(this.buffer, 0, GifConstants.NetscapeLoopingSubBlockSize);
                        this.gifMetadata.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.AsSpan(1)).RepeatCount;
                        this.stream.Skip(1); // Skip the terminator.
                        return;
                    }

                    // Could be something else not supported yet.
                    // Skip the subblock and terminator.
                    this.SkipBlock(subBlockSize);
                }

                return;
            }

            this.SkipBlock(appLength); // Not supported by any known decoder.
        }