/// <summary>
/// Losslessly transform the JPEG image associated with this transformer instance into one or more JPEG images
/// stored in the given destination buffers. Lossless transforms work by moving the raw coefficients from one
/// JPEG image structure to another without altering the values of the coefficients. While this is typically
/// faster than decompressing the image, transforming it, and re-compressing it, lossless transforms are not
/// free. Each lossless transform requires reading and performing Huffman decoding on all of the coefficients
/// in the source image, regardless of the size of the destination image, thus this method provides a means of
/// generating multiple transformed images from the same source or of applying multiple transformations
/// simultaneously, in order to eliminate the need to read the source coefficients multiple times.
/// </summary>
/// <param name="destBuffers">
/// An array of image buffers. <paramref name="destBuffers" />[i] will receive a JPEG image that has been
/// transformed using the parameters in <paramref name="transforms" />[i]. Use
/// <see cref="NativeMethods.bufSize" /> to determine the maximum size for each buffer based on the
/// transformed or cropped width and height and the chroma subsampling used in the source image.
/// </param>
/// <param name="transforms">An array of <seealso cref="TurboJpegTransform" /> instances, each of which
/// specifies the transform parameters and/or cropping region for the corresponding transformed output image.
/// </param>
/// <param name="options">The flags to use for the transforms.</param>
public void Transform(byte[][] destBuffers, TurboJpegTransform[] transforms, TurboJpegFlags options)
{
Contract.Requires(destBuffers != null);
Contract.Requires(transforms != null);
Contract.Requires(transforms.Length == destBuffers.Length);
Contract.Requires(Enum.IsDefined(typeof(TransformOptions), options));
Contract.Ensures(Contract.ForAll(destBuffers, _ => _ != null));
Contract.Assume(this.JpegBuffer != null, "JPEG buffer not initialized");
var count = destBuffers.Length;
var destBufferPtrs = new IntPtr[count];
this.transformedSizes = new int[count];
if (NativeMethods.transform(this.Handle,
this.JpegBuffer,
this.JpegSize,
count,
ref destBufferPtrs,
ref this.transformedSizes,
transforms,
options) != 0)
{
throw new Exception(TurboJpegInterop.GetLastError());
}
// we now have the result in buffers on the unmanaged heap
for (var i = 0; i < count; ++i)
{
destBuffers[i] = new byte[this.transformedSizes[i]];
Marshal.Copy(destBufferPtrs[i], destBuffers[i], 0, this.transformedSizes[i]);
}
}
/// <summary>
/// Decompress the JPEG source image associated with this decompressor instance and output a YUV planar image to the given
/// destination buffer. This method performs JPEG decompression but leaves out the colour conversion step, so a planar YUV
/// image is generated instead of an RGB image. The padding of the planes in this image is the same as in the images
/// generated by <seealso cref="TurboJpegCompressor#EncodeYuv(byte[], int)" />.
/// <para>
/// NOTE: Technically, the JPEG format uses the YCbCr colourspace, but per the convention of the digital video
/// community, the TurboJPEG API uses "YUV" to refer to an image format consisting of Y, Cb, and Cr image planes.
/// </para>
/// </summary>
/// <param name="flags">The <see cref="TurboJpegFlags" /> controlling decompression.</param>
public TurboJpegBuffer DecompressToYuv(TurboJpegFlags flags)
{
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 bufferSize = NativeMethods.bufSizeYUV(this.jpegWidth, 4, this.jpegHeight, this.jpegSubsampling);
using (var buffer = new TurboJpegSafeHandle(NativeMethods.alloc(bufferSize)))
{
var ptr = buffer.DangerousGetHandle();
if (NativeMethods.decompressToYUV(this.Handle,
this.jpegBuffer,
this.jpegBuffer.Length,
ref ptr,
this.jpegWidth,
4,
this.jpegHeight,
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>
/// 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>
/// Losslessly transform the JPEG image associated with this transformer instance and return an array of
/// <seealso cref="TurboJpegDecompressor" /> instances, each of which has a transformed JPEG image associated
/// with it.
/// </summary>
/// <param name="transforms">An array of <see cref="TurboJpegTransform" /> instances, each of which specifies
/// the transform parameters and/or cropping region for the corresponding transformed output image.</param>
/// <param name="flags">The flags to use when transforming.</param>
/// <param name="preallocateBuffers">If set to <c>true</c>, preallocate buffers.</param>
/// <returns>
/// An array of <seealso cref="TurboJpegDecompressor" /> instances, each of which has a transformed
/// JPEG image associated with it.
/// </returns>
public TurboJpegDecompressor[] Transform(TurboJpegTransform[] transforms, TurboJpegFlags flags, bool preallocateBuffers)
{
Contract.Requires(transforms != null);
Contract.Requires(Enum.IsDefined(typeof(TransformOptions), flags));
Contract.Ensures(Contract.Result <TurboJpegDecompressor[]>() != null);
Contract.Ensures(Contract.Result <TurboJpegDecompressor[]>().Length == transforms.Length);
Contract.Ensures(Contract.ForAll(Contract.Result <TurboJpegDecompressor[]>(), _ => _ != null));
var count = transforms.Length;
var destinationBuffers = new byte[count][];
Contract.Assume(this.Width > 0, "JPEG buffer not initialized");
Contract.Assume(this.Height > 0, "JPEG buffer not initialized");
var decompressors = new TurboJpegDecompressor[count];
if (preallocateBuffers)
{
for (var i = 0; i < count; i++)
{
var width = this.Width;
var height = this.Height;
if ((transforms[i].Options & TransformOptions.Crop) != 0)
{
if (transforms[i].Width != 0)
{
width = transforms[i].Width;
}
if (transforms[i].Height != 0)
{
height = transforms[i].Height;
}
}
destinationBuffers[i] = new byte[NativeMethods.bufSize(width, height, this.Subsampling)];
}
this.Transform(destinationBuffers, transforms, flags);
for (var i = 0; i < count; i++)
{
decompressors[i] = new TurboJpegDecompressor(destinationBuffers[i]);
}
}
else
{
var destBufferPtrs = new IntPtr[count];
this.transformedSizes = new int[count];
if (NativeMethods.transform(this.Handle,
this.JpegBuffer,
this.JpegSize,
count,
ref destBufferPtrs,
ref this.transformedSizes,
transforms,
flags) != 0)
{
throw new Exception(TurboJpegInterop.GetLastError());
}
// we now have the result in buffers on the unmanaged heap
for (var i = 0; i < count; ++i)
{
decompressors[i] = new TurboJpegDecompressor();
decompressors[i].SetJpegImage(destBufferPtrs[i]);
}
}
return(decompressors);
}
