A callback function that can be used to modify the DCT coefficients
after they are losslessly transformed but before they are transcoded to a
new JPEG file. This allows for custom filters or other transformations to
be applied in the frequency domain.
@param coeffs pointer to an array of transformed DCT coefficients. (NOTE:
this pointer is not guaranteed to be valid once the callback
returns, so applications wishing to hand off the DCT coefficients
to another function or library should make a copy of them within
the body of the callback.)
@param arrayRegion #tjregion structure containing the width and height of
the array pointed to by <tt>coeffs</tt> as well as its offset
relative to the component plane. TurboJPEG implementations may
choose to split each component plane into multiple DCT coefficient
arrays and call the callback function once for each array.
@param planeRegion #tjregion structure containing the width and height of
the component plane to which <tt>coeffs</tt> belongs
@param componentID ID number of the component plane to which
<tt>coeffs</tt> belongs (Y, U, and V have, respectively, ID's of
0, 1, and 2 in typical JPEG images.)
@param transformID ID number of the transformed image to which
<tt>coeffs</tt> belongs. This is the same as the index of the
transform in the <tt>transforms</tt> array that was passed to
#tjTransform().
@param transform a pointer to a #tjtransform structure that specifies the
parameters and/or cropping region for this transform
@return 0 if the callback was successful, or -1 if an error occurred.
A callback function that can be used to modify the DCT coefficients after they are losslessly transformed but before they are transcoded to a new JPEG file. This allows for custom filters or other transformations to be applied in the frequency domain.
@param coeffs pointer to an array of transformed DCT coefficients. (NOTE: this pointer is not guaranteed to be valid once the callback returns, so applications wishing to hand off the DCT coefficients to another function or library should make a copy of them within the body of the callback.) @param arrayRegion #tjregion structure containing the width and height of the array pointed to by <tt>coeffs</tt> as well as its offset relative to the component plane. TurboJPEG implementations may choose to split each component plane into multiple DCT coefficient arrays and call the callback function once for each array. @param planeRegion #tjregion structure containing the width and height of the component plane to which <tt>coeffs</tt> belongs @param componentID ID number of the component plane to which <tt>coeffs</tt> belongs (Y, U, and V have, respectively, ID's of 0, 1, and 2 in typical JPEG images.) @param transformID ID number of the transformed image to which <tt>coeffs</tt> belongs. This is the same as the index of the transform in the <tt>transforms</tt> array that was passed to #tjTransform(). @param transform a pointer to a #tjtransform structure that specifies the parameters and/or cropping region for this transform
@return 0 if the callback was successful, or -1 if an error occurred.