Exemplo n.º 1
0
        /// <summary>
        /// Processes the Start of Frame marker.  Specified in section B.2.2.
        /// </summary>
        /// <param name="remaining">The remaining bytes in the segment block.</param>
        private void ProcessStartOfFrameMarker(int remaining)
        {
            if (this.ComponentCount != 0)
            {
                throw new ImageFormatException("Multiple SOF markers");
            }

            switch (remaining)
            {
            case 6 + (3 * 1):     // Grayscale image.
                this.ComponentCount = 1;
                break;

            case 6 + (3 * 3):     // YCbCr or RGB image.
                this.ComponentCount = 3;
                break;

            case 6 + (3 * 4):     // YCbCrK or CMYK image.
                this.ComponentCount = 4;
                break;

            default:
                throw new ImageFormatException("Incorrect number of components");
            }

            this.InputProcessor.ReadFull(this.Temp, 0, remaining);

            // We only support 8-bit precision.
            if (this.Temp[0] != 8)
            {
                throw new ImageFormatException("Only 8-Bit precision supported.");
            }

            int height = (this.Temp[1] << 8) + this.Temp[2];
            int width  = (this.Temp[3] << 8) + this.Temp[4];

            this.ImageSizeInPixels = new Size(width, height);

            if (this.Temp[5] != this.ComponentCount)
            {
                throw new ImageFormatException("SOF has wrong length");
            }

            this.Components = new OrigComponent[this.ComponentCount];

            for (int i = 0; i < this.ComponentCount; i++)
            {
                byte componentIdentifier = this.Temp[6 + (3 * i)];
                var  component           = new OrigComponent(componentIdentifier, i);
                component.InitializeCoreData(this);
                this.Components[i] = component;
            }

            int h0 = this.Components[0].HorizontalSamplingFactor;
            int v0 = this.Components[0].VerticalSamplingFactor;

            this.ImageSizeInMCU = this.ImageSizeInPixels.DivideRoundUp(8 * h0, 8 * v0);

            foreach (OrigComponent component in this.Components)
            {
                component.InitializeDerivedData(this);
            }

            this.ColorSpace = this.DeduceJpegColorSpace();
        }