/// <summary>
/// Decompress the JPEG source image associated with this decompressor instance and output a decompressed image to
/// the given destination buffer.
/// </summary>
/// <param name="desiredWidth">The desired width (in pixels) of the decompressed image. If the desired image
/// dimensions are different than the dimensions of the JPEG image being decompressed, then TurboJPEG will use
/// scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired
/// dimensions. Setting this to 0 is the same as setting it to the width of the JPEG image; in other words the
/// width will not be considered when determining the scaled image size).
/// </param>
/// <param name="pitch">The number of bytes per line of the destination image. Normally, this should be set to
/// <code>scaledWidth * <see cref="TurboJpegUtilities.GetPixelSize" />(pixelFormat)</code> if the decompressed
/// image is unpadded, but you can use this to, for instance, pad each line of the decompressed image to a
/// 4-byte boundary or to decompress the JPEG image into a region of a larger image. NOTE: <code>scaledWidth</code>
/// can be determined by calling
/// <code>scalingFactor.<seealso cref="TurboJpegScalingFactor#getScaled getScaled" />(jpegWidth)</code> or by
/// calling <seealso cref="GetScaledWidth" />. Setting this parameter to 0 is the equivalent of setting it to
/// <code>scaledWidth * <see cref="TurboJpegUtilities.GetPixelSize" />(pixelFormat)</code>.</param>
/// <param name="desiredHeight">
/// The desired Height (in pixels) of the decompressed image (or image region.) If the desired
/// image dimensions are different than the dimensions of the JPEG image being decompressed, then TurboJPEG will use
/// scaling in the JPEG decompressor to generate the largest possible image that will fit within the desired dimensions.
/// Setting this to 0 is the same as setting it to the Height of the JPEG image (in other words, the Height will not be
/// considered when determining the scaled image size.)
/// </param>
/// <param name="pixelFormat">
/// pixel format of the decompressed/decoded image (one of
/// <seealso cref="TurboJpegUtilities#Rgb TurboJpegUtilities.PF_*" />)
/// </param>
/// <param name="flags">
/// the bitwise OR of one or more of
/// <seealso cref="TurboJpegUtilities#BottomUp TurboJpegUtilities.FLAG_*" />
/// </param>
public TurboJpegBuffer Decompress(int desiredWidth,
int pitch,
int desiredHeight,
PixelFormat pixelFormat,
TurboJpegFlags flags)
{
Contract.Requires(desiredWidth >= 0, "desiredWidth must be non-negative");
Contract.Requires(desiredHeight >= 0, "desiredHeight must be non-negative");
Contract.Requires(pitch >= 0, "pitch must be non-negative");
Contract.Requires(Enum.IsDefined(typeof(TurboJpegFlags), flags));
Contract.Ensures(Contract.Result <TurboJpegBuffer>()
.BufferSize > 0,
"output buffer must have non-zero size");
Contract.Assume(this.jpegBuffer != null, "No JPEG image is associated with this instance");
var pixelSize = TurboJpegUtilities.GetPixelSize(pixelFormat);
var scaledWidth = this.GetScaledWidth(desiredWidth, desiredHeight);
var scaledHeight = this.GetScaledHeight(desiredWidth, desiredHeight);
if (pitch == 0)
{
pitch = scaledWidth * pixelSize;
}
var bufferSize = pitch * scaledHeight;
// having allocated memory with the libjpeg-turbo allocator, we must ensure that we release it with the
// matching deallocator lest Bad Things happen. Unlike compress, where the initial buffer size is a best
// guess, we know the dimensions of the uncompressed image and the number of bits per pixel and so sizing
// it appropriately is trivial and the buffer will never be reallocated
using (var buffer = new TurboJpegSafeHandle(NativeMethods.alloc(bufferSize)))
{
var ptr = buffer.DangerousGetHandle();
if (NativeMethods.decompress(this.Handle,
this.jpegBuffer,
this.jpegBuffer.Length,
ptr,
desiredWidth,
pitch,
desiredHeight,
pixelFormat,
flags) != 0)
{
throw new Exception(TurboJpegInterop.GetLastError());
}
// we now have the result in a buffer on the unmanaged heap.
return(new TurboJpegBuffer(ptr, bufferSize));
}
}
/// <summary>
/// Associate an uncompressed source image with this compressor instance.
/// </summary>
/// <param name="sourceImage">Image buffer containing RGB or grayscale pixels to be compressed or encoded.</param>
/// <param name="x">X offset (in pixels) of the region in the source image from which the JPEG or YUV image
/// should be compressed/encoded.</param>
/// <param name="y">Y offset (in pixels) of the region in the source image from which the JPEG or YUV image
/// should be compressed/encoded.</param>
/// <param name="width">Width (in pixels) of the region in the source image from which the JPEG or YUV image
/// should be compressed/encoded.</param>
/// <param name="pitch">Bytes per line of the source image. Normally, this should be
/// <code>width * <see cref="TurboJpegUtilities.GetPixelSize"/>(<paramref name="pixelFormat"/>)</code> if the
/// source image is unpadded, but you can use this parameter to, for instance, specify that the scanlines in
/// the source image are padded to a 4-byte boundary or to compress/encode a JPEG or YUV image from a region
/// of a larger source image. You can also be clever and use this parameter to skip lines, etc. Setting this
/// parameter to 0 is the equivalent of setting it to
/// <code>width * <see cref="TurboJpegUtilities.GetPixelSize"/>(<paramref name="pixelFormat"/>)</code>.
/// </param>
/// <param name="height">Height (in pixels) of the region in the source image from which the JPEG or YUV image
/// should be compressed/encoded.</param>
/// <param name="pixelFormat">Pixel format of the source image.</param>
public void SetSourceImage(byte[] sourceImage,
int x,
int y,
int width,
int pitch,
int height,
PixelFormat pixelFormat)
{
Contract.Requires(sourceImage != null, "sourceImage must not be null");
Contract.Requires(x >= 0, "x must be non-negative");
Contract.Requires(y >= 0, "y must be non-negative");
Contract.Requires(width > 0, "width must be greater than zero");
Contract.Requires(height > 0, "height must be greater than zero");
Contract.Requires(pitch >= 0, "pitch must be non-negative");
this.sourceBuffer = sourceImage;
this.sourceWidth = width;
this.sourcePitch = pitch == 0 ? width * TurboJpegUtilities.GetPixelSize(pixelFormat) : pitch;
this.sourceHeight = height;
this.sourcePixelFormat = pixelFormat;
this.sourceX = x;
this.sourceY = y;
}
