コード例 #1
0
        /// <summary>
        /// Reads the tga file header from the stream.
        /// </summary>
        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
        /// <returns>The image origin.</returns>
        private TgaImageOrigin ReadFileHeader(Stream stream)
        {
            this.currentStream = stream;

            Span <byte> buffer = stackalloc byte[TgaFileHeader.Size];

            this.currentStream.Read(buffer, 0, TgaFileHeader.Size);
            this.fileHeader  = TgaFileHeader.Parse(buffer);
            this.metadata    = new ImageMetadata();
            this.tgaMetadata = this.metadata.GetTgaMetadata();
            this.tgaMetadata.BitsPerPixel = (TgaBitsPerPixel)this.fileHeader.PixelDepth;

            var alphaBits = this.fileHeader.ImageDescriptor & 0xf;

            if (alphaBits != 0 && alphaBits != 1 && alphaBits != 8)
            {
                TgaThrowHelper.ThrowImageFormatException("Invalid alpha channel bits");
            }

            this.tgaMetadata.AlphaChannelBits = (byte)alphaBits;
            this.hasAlpha = alphaBits > 0;

            // Bits 4 and 5 describe the image origin.
            var origin = (TgaImageOrigin)((this.fileHeader.ImageDescriptor & 0x30) >> 4);

            return(origin);
        }
コード例 #2
0
        /// <summary>
        /// Reads the tga file header from the stream.
        /// </summary>
        /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
        /// <returns>true, if the image origin is top left.</returns>
        private bool ReadFileHeader(Stream stream)
        {
            this.currentStream = stream;

            Span <byte> buffer = stackalloc byte[TgaFileHeader.Size];

            this.currentStream.Read(buffer, 0, TgaFileHeader.Size);
            this.fileHeader  = TgaFileHeader.Parse(buffer);
            this.metadata    = new ImageMetadata();
            this.tgaMetadata = this.metadata.GetTgaMetadata();
            this.tgaMetadata.BitsPerPixel = (TgaBitsPerPixel)this.fileHeader.PixelDepth;

            var alphaBits = this.fileHeader.ImageDescriptor & 0xf;

            if (alphaBits != 0 && alphaBits != 1 && alphaBits != 8)
            {
                TgaThrowHelper.ThrowImageFormatException("Invalid alpha channel bits");
            }

            this.tgaMetadata.AlphaChannelBits = (byte)alphaBits;
            this.hasAlpha = alphaBits > 0;

            // TODO: bits 4 and 5 describe the image origin. See spec page 9. bit 4 is currently ignored.
            // Theoretically the origin could also be top right and bottom right.
            // Bit at position 5 of the descriptor indicates, that the origin is top left instead of bottom left.
            if ((this.fileHeader.ImageDescriptor & (1 << 5)) != 0)
            {
                return(true);
            }

            return(false);
        }
コード例 #3
0
ファイル: TgaDecoder.cs プロジェクト: wilka/ImageSharp
        /// <inheritdoc/>
        public Image <TPixel> Decode <TPixel>(Configuration configuration, Stream stream)
            where TPixel : unmanaged, IPixel <TPixel>
        {
            Guard.NotNull(stream, nameof(stream));

            var decoder = new TgaDecoderCore(configuration, this);

            try
            {
                return(decoder.Decode <TPixel>(stream));
            }
            catch (InvalidMemoryOperationException ex)
            {
                Size dims = decoder.Dimensions;

                TgaThrowHelper.ThrowInvalidImageContentException($"Can not decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);

                // Not reachable, as the previous statement will throw a exception.
                return(null);
            }
        }
コード例 #4
0
        /// <summary>
        /// Decodes the image from the specified stream.
        /// </summary>
        /// <typeparam name="TPixel">The pixel format.</typeparam>
        /// <param name="stream">The stream, where the image should be decoded from. Cannot be null.</param>
        /// <exception cref="System.ArgumentNullException">
        ///    <para><paramref name="stream"/> is null.</para>
        /// </exception>
        /// <returns>The decoded image.</returns>
        public Image <TPixel> Decode <TPixel>(Stream stream)
            where TPixel : unmanaged, IPixel <TPixel>
        {
            try
            {
                TgaImageOrigin origin = this.ReadFileHeader(stream);
                this.currentStream.Skip(this.fileHeader.IdLength);

                // Parse the color map, if present.
                if (this.fileHeader.ColorMapType != 0 && this.fileHeader.ColorMapType != 1)
                {
                    TgaThrowHelper.ThrowNotSupportedException($"Unknown tga colormap type {this.fileHeader.ColorMapType} found");
                }

                if (this.fileHeader.Width == 0 || this.fileHeader.Height == 0)
                {
                    throw new UnknownImageFormatException("Width or height cannot be 0");
                }

                var image = Image.CreateUninitialized <TPixel>(this.configuration, this.fileHeader.Width, this.fileHeader.Height, this.metadata);
                Buffer2D <TPixel> pixels = image.GetRootFramePixelBuffer();

                if (this.fileHeader.ColorMapType == 1)
                {
                    if (this.fileHeader.CMapLength <= 0)
                    {
                        TgaThrowHelper.ThrowImageFormatException("Missing tga color map length");
                    }

                    if (this.fileHeader.CMapDepth <= 0)
                    {
                        TgaThrowHelper.ThrowImageFormatException("Missing tga color map depth");
                    }

                    int colorMapPixelSizeInBytes = this.fileHeader.CMapDepth / 8;
                    int colorMapSizeInBytes      = this.fileHeader.CMapLength * colorMapPixelSizeInBytes;
                    using (IManagedByteBuffer palette = this.memoryAllocator.AllocateManagedByteBuffer(colorMapSizeInBytes, AllocationOptions.Clean))
                    {
                        this.currentStream.Read(palette.Array, this.fileHeader.CMapStart, colorMapSizeInBytes);

                        if (this.fileHeader.ImageType == TgaImageType.RleColorMapped)
                        {
                            this.ReadPalettedRle(
                                this.fileHeader.Width,
                                this.fileHeader.Height,
                                pixels,
                                palette.Array,
                                colorMapPixelSizeInBytes,
                                origin);
                        }
                        else
                        {
                            this.ReadPaletted(
                                this.fileHeader.Width,
                                this.fileHeader.Height,
                                pixels,
                                palette.Array,
                                colorMapPixelSizeInBytes,
                                origin);
                        }
                    }

                    return(image);
                }

                // Even if the image type indicates it is not a paletted image, it can still contain a palette. Skip those bytes.
                if (this.fileHeader.CMapLength > 0)
                {
                    int colorMapPixelSizeInBytes = this.fileHeader.CMapDepth / 8;
                    this.currentStream.Skip(this.fileHeader.CMapLength * colorMapPixelSizeInBytes);
                }

                switch (this.fileHeader.PixelDepth)
                {
                case 8:
                    if (this.fileHeader.ImageType.IsRunLengthEncoded())
                    {
                        this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 1, origin);
                    }
                    else
                    {
                        this.ReadMonoChrome(this.fileHeader.Width, this.fileHeader.Height, pixels, origin);
                    }

                    break;

                case 15:
                case 16:
                    if (this.fileHeader.ImageType.IsRunLengthEncoded())
                    {
                        this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 2, origin);
                    }
                    else
                    {
                        this.ReadBgra16(this.fileHeader.Width, this.fileHeader.Height, pixels, origin);
                    }

                    break;

                case 24:
                    if (this.fileHeader.ImageType.IsRunLengthEncoded())
                    {
                        this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 3, origin);
                    }
                    else
                    {
                        this.ReadBgr24(this.fileHeader.Width, this.fileHeader.Height, pixels, origin);
                    }

                    break;

                case 32:
                    if (this.fileHeader.ImageType.IsRunLengthEncoded())
                    {
                        this.ReadRle(this.fileHeader.Width, this.fileHeader.Height, pixels, 4, origin);
                    }
                    else
                    {
                        this.ReadBgra32(this.fileHeader.Width, this.fileHeader.Height, pixels, origin);
                    }

                    break;

                default:
                    TgaThrowHelper.ThrowNotSupportedException("ImageSharp does not support this kind of tga files.");
                    break;
                }

                return(image);
            }
            catch (IndexOutOfRangeException e)
            {
                throw new ImageFormatException("TGA image does not have a valid format.", e);
            }
        }