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diff --git a/src/imageplugins/noisereduction/noisereduction.h b/src/imageplugins/noisereduction/noisereduction.h new file mode 100644 index 00000000..69e14123 --- /dev/null +++ b/src/imageplugins/noisereduction/noisereduction.h @@ -0,0 +1,257 @@ +/* ============================================================ + * + * This file is a part of digiKam project + * http://www.digikam.org + * + * Date : 2005-05-25 + * Description : Noise Reduction threaded image filter. + * + * Copyright (C) 2005-2007 by Gilles Caulier <caulier dot gilles at gmail dot com> + * + * Original Noise Filter algorithm copyright (C) 2005 + * Peter Heckert <peter dot heckert at arcor dot de> + * from dcamnoise2 gimp plugin available at this url : + * http://home.arcor.de/peter.heckert/dcamnoise2-0.63.c + * + * This program is free software; you can redistribute it + * and/or modify it under the terms of the GNU General + * Public License as published by the Free Software Foundation; + * either version 2, or (at your option) + * any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * ============================================================ */ + +#ifndef NOISE_REDUCTION_H +#define NOISE_REDUCTION_H + +// C++ includes. + +#include <cmath> + +// Digikam includes. + +#include "dimgthreadedfilter.h" + +/**============= NOTICE TO USE THE FILTER =============================================================== + * + * Let me explain, how the filter works, some understanding is necessary to use it: + * + * Hint for the novice user: + * In most cases only Filter Max Radius, Filter treshold and Texture Detail are needed and the other + * params can be left at their default setting. + * + * Main Filter (Preprocessing) + * First, a filtered template is generated, using an adaptive filter. + * To see this template, we must set _Luminance tolerance, _Color tolerance to 1.0. + *------------------------------------------------------------------------------------------------------------ + * + * "Filter max. Radius" is preset to 5.0 + * This is good for most noise situations. + * In any case it must be about the same size as noise granularity ore somewhat more. + * If it is set higher than necessary, then it can cause unwanted blur. + *------------------------------------------------------------------------------------------------------------ + * + * "Filter Threshold" should be set so that edges are clearly visible and noise is smoothed out. + * This threshold value is not bound to any intensity value, it is bound to the second derivative of + * intensity values. + * Simply adjust it and watch the preview. Adjustment must be made carefully, because the gap + * between "noisy", "smooth", and "blur" is very small. Adjust it as carefully as you would adjust + * the focus of a camera. + *------------------------------------------------------------------------------------------------------------ + * + * "Lookahead" defines the pixel distance in which the filter looks ahead for luminance variations + * Normally the default value should do. + * When _Lookahead is increased, then spikenoise is erased. + * Eventually readjust Filter treshold, when you changed lookahead. + * When the value is to high, then the adaptive filter cannot longer accurately track image details, and + * noise can reappear or blur can occur. + * + * Minimum value is 1.0, this gives best accuracy when blurring very weak noise. + * + * I never had good success with other values than 2.0. + * However, for images with extemely high or low resolution another value possibly is better. + * Use it only as a last ressort. + *------------------------------------------------------------------------------------------------------------ + * + * "Phase Jitter Damping" defines how fast the adaptive filter-radius reacts to luminance variations. + * I have preset a value, that should do in most cases. + * If increased, then edges appear smoother, if too high, then blur may occur. + * If at minimum then noise and phase jitter at edges can occur. + * It can suppress Spike noise when increased and this is the preferred method to remove spike noise. + *------------------------------------------------------------------------------------------------------------ + * + * "Sharpness" does just what it says, it improves sharpness. It improves the frequency response for the filter. + * When it is too strong then not all noise can be removed, or spike noise may appear. + * Set it near to maximum, if you want to remove weak noise or JPEG-artifacts, without loosing detail. + *------------------------------------------------------------------------------------------------------------ + * + * "Erosion". The new filter gives better sharpness and this also gives problems + * with spike noise. The Erosion param erodes singular spikes and it has a smooth effect to edges, and sharpens + * edges by erosion, so noise at edges is eroded. + * The effect is dependant from sharpness,phase-jitter damping and lookahead. + * Set it to minimum (zero), if you want to remove weak noise or JPEG-artifacts. + * When "Erosion" is increased, then also increasing "Phase Jitter Damping" is often useful + * + * It works nicely. Apart from removing spike noise it has a sharpening and antialiasing effect to edges + * (Sharpening occurs by erosion, not by deconvolution) + *------------------------------------------------------------------------------------------------------------ + * + * "Texture Detail" can be used, to get more or less texture accuracy. + * When decreased, then noise and texture are blurred out, when increased then texture is + * amplified, but also noise will increase. + * It has almost no effect to image edges, opposed to Filter theshold, which would blur edges, when increased. + * + * E.g. if Threshold is adjusted in away so that edges are sharp, and there is still too much area noise, then + * Texture detail could be used to reduce noise without blurring edges. + * (Another way would be to decrease radius and to increase threshold) + * + *------------------------------------------------------------------------------------------------------------ + * + * The filtered image that is now seen in the preview, is used as template for the following processing steps, + * therefore it is important to do this adjustment in first place and to do it as good as possible. + *------------------------------------------------------------------------------------------------------------ + * + * Combining original image and filtered image, using tolerance thresholds (Postprocessing) + * This can give a final touch of sharpness to your image. + * It is not necessary to do this, if you want to reduce JPEG-artifacts or weak noise. + * It's purpose is to master strong noise without loosing too much sharpness. + * + * Note, that this all is done in one filter invocation. Preprocessing and postprocessing is done in one run, + * but logically and in the algorithm they are different and ordered processes. + * + * + * Adjust _Color tolerance or/and Luminance tolerance, (if necessary) so that you get the final image. + * I recommend to use only one, either _Color or _Luminance. + * These settings do not influence the main smoothing process. What they really do is this: + * + * The tolerance values are used as error-thresholds to compare the filtered template with the original + * image. The plugin algorithm uses them to combine the filtered template with the original image + * so that noise and filter errors (blur) are thrown out. + * A filtered pixel, that is too far away from the original pixel will be overridden by original image content. + * + * Hint: + * If you cange other sliders, like lookahead or Texture Detail, then you should set color tolerance and + * luminance tolerance to 1.0 (right end), because otherwise the filtered template is partially hidden + * and e.g. the effects for the damping filter cant be seen clearly and cant be optimized. + *------------------------------------------------------------------------------------------------------------ + * + * _Gamma can be used to increase the tolerance values for darker areas (which commonly are more noisy) + * This results in more blur for shadow areas. + * + * Hint for users of previous versions: + * Gamma also influences the main-filter process. While the previous version did not have this feature, + * I have reimplemented it, however, the algorithm used is totally new. + * + * + * Keep in mind, how the filter works, then usage should be easy! + * + * + * ================ THEORY AND TECHNIC ======================================================================= + * + * Some interesting things (theoretic and technic) + * This plugin bases on the assumption, that noise has no 2-dimensional correlation and therefore + * can be removed in a 1-dimensional process. + * To remove noise, I use a four-times boxfilter with variable radius. + * + * The radius is calculated from 2nd derivative of pixeldata. + * A gauss filter is used to calculte 2nd derivative. + * The filter has some inbuilt features to clip low amplitude noise to clip very high values that would + * slow down response time. + * The 2nd derivative is lowpassfiltered and then radius is calculated as (Filter Treshold)/2nd_derivative. + * The radius modulation data is precalulated and buffered an is used to steer filter radius when + * the actual filtering occurs. + * + * Noise and texture can be further suppressed by nonlinear distortion before adaptive filtering. + * To make this possible I subtract low frequency from image data before denoising, so that I get a + * bipolar, zerosymmetric image signal. + * + * The filter works in a /one-dimensional/ way. It is applied to x and then to y axis. + * + * After filtering a zerodimensional point operator (pixel by pixel comparison) is used, where + * filter-errors are thrown out. + * This is meant to limit and control filter errors,it can give "final touch" to the image, but it has + * nothing to do with the main filter process. + * + * I do not know if something like this filter already exists. + * It is all based on my own ideas and experiments. + * Possibly a separable adaptive gauss-filter is a new thing. + * Also it is an impossible thing, from a mathemathical point of view ;-) + * It is possible only for bandwidth limited images. + * Happyly most photographic images are bandwidth limited, or when they are noisy then we want + * to limit banwith locally. And this is, what the filter does: It limits bandwidth locally, dependent + * from (approximately) 2nd derivative of intensity. + * + * Because gauss filtering is essentially linear diffusion, and because this filter uses a variable + * nonlinear modulated gaussfilter (four box passes are almost gauss) we could say, that this filter + * implements a special subclass of nonlinear adaptive diffusion, which is separable, and indeed, + * results are very similar to nonlinear diffusion filters. + * However, because the filter is separable, it is much faster and needs less memory. + */ + +namespace DigikamNoiseReductionImagesPlugin +{ + +class NoiseReduction : public Digikam::DImgThreadedFilter +{ + +public: + + NoiseReduction(Digikam::DImg *orgImage, TQObject *parent, + double radius, double lsmooth, double effect, double texture, double sharp, + double csmooth, double lookahead, double gamma, double damping, double phase); + ~NoiseReduction(){}; + +private: + + void filterImage(void); + + void iir_init(double r); + void box_filter(double *src, double *end, double *dest, double radius); + void iir_filter(float* const start, float* const end, float* dstart, double radius, const int type); + void filter(float *buffer, float *data, float *data2, float *rbuf, float *tbuf, int width, int color); + void blur_line(float* const data, float* const data2, float* const buffer, + float* rbuf, float* tbuf, const uchar *src, uchar *dest, int len); + + inline double mypow(double val, double ex) + { + if (fabs(val) < 1e-16) return 0.0; + if (val > 0.0) return exp(log(val)*ex); + return -exp(log(-val)*ex); + }; + +private: + + struct iir_param + { + double B, b1, b2, b3, b0, r, q; + double *p; + } m_iir; + + enum IIRFilteringMode + { + Gaussian=0, + SecondDerivative + }; + + int m_clampMax; + + double m_radius; + double m_lsmooth; + double m_csmooth; + double m_effect; + double m_lookahead; + double m_gamma; + double m_damping; + double m_phase; + double m_texture; + double m_sharp; +}; + +} // NameSpace DigikamNoiseReductionImagesPlugin + +#endif /* NOISE_REDUCTION_H */ |