// Copyright (C) 2006  Davis E. King (davis@dlib.net)
// License: Boost Software License   See LICENSE.txt for the full license.
#undef DLIB_SPATIAL_FILTERINg_ABSTRACT_
#ifdef DLIB_SPATIAL_FILTERINg_ABSTRACT_

#include "../pixel.h"
#include "../matrix.h"

namespace dlib
{

// ----------------------------------------------------------------------------------------

    template <
        typename in_image_type,
        typename out_image_type,
        typename EXP,
        typename T
        >
    rectangle spatially_filter_image (
        const in_image_type& in_img,
        out_image_type& out_img,
        const matrix_exp<EXP>& filter,
        T scale = 1,
        bool use_abs = false,
        bool add_to = false
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type>::has_alpha == false
            - pixel_traits<typename out_image_type::type>::has_alpha == false 
            - is_same_object(in_img, out_img) == false 
            - T must be some scalar type
            - filter.size() != 0
            - scale != 0
            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
                - use_abs == false && add_to == false
                  (i.e. You can only use the use_abs and add_to options with grayscale images)
        ensures
            - Applies the given spatial filter to in_img and stores the result in out_img (i.e.
              cross-correlates in_img with filter).  Also divides each resulting pixel by scale.  
            - The intermediate filter computations will be carried out using variables of type EXP::type.
              This is whatever scalar type is used inside the filter matrix. 
            - Pixel values are stored into out_img using the assign_pixel() function and therefore
              any applicable color space conversion or value saturation is performed.  Note that if 
              add_to is true then the filtered output value will be added to out_img rather than 
              overwriting the original value.
            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
                - The filter is applied to each color channel independently.
            - if (use_abs == true) then
                - pixel values after filtering that are < 0 are converted to their absolute values.
            - The filter is applied such that it's centered over the pixel it writes its
              output into.  For centering purposes, we consider the center element of the
              filter to be filter(filter.nr()/2,filter.nc()/2).  This means that the filter
              that writes its output to a pixel at location point(c,r) and is W by H (width
              by height) pixels in size operates on exactly the pixels in the rectangle
              centered_rect(point(c,r),W,H) within in_img.
            - Pixels close enough to the edge of in_img to not have the filter still fit 
              inside the image are always set to zero.
            - #out_img.nc() == in_img.nc()
            - #out_img.nr() == in_img.nr()
            - returns a rectangle which indicates what pixels in #out_img are considered 
              non-border pixels and therefore contain output from the filter.
            - if (use_abs == false && all images and filers contain float types) then
                - This function will use SIMD instructions and is particularly fast.  So if
                  you can use this form of the function it can give a decent speed boost.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename in_image_type,
        typename out_image_type,
        typename EXP1,
        typename EXP2,
        typename T
        >
    rectangle spatially_filter_image_separable (
        const in_image_type& in_img,
        out_image_type& out_img,
        const matrix_exp<EXP1>& row_filter,
        const matrix_exp<EXP2>& col_filter,
        T scale = 1,
        bool use_abs = false,
        bool add_to = false
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type>::has_alpha == false
            - pixel_traits<typename out_image_type::type>::has_alpha == false 
            - is_same_object(in_img, out_img) == false 
            - T must be some scalar type
            - scale != 0
            - row_filter.size() != 0
            - col_filter.size() != 0
            - is_vector(row_filter) == true
            - is_vector(col_filter) == true
            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
                - use_abs == false && add_to == false
                  (i.e. You can only use the use_abs and add_to options with grayscale images)
        ensures
            - Applies the given separable spatial filter to in_img and stores the result in out_img.  
              Also divides each resulting pixel by scale.  Calling this function has the same
              effect as calling the regular spatially_filter_image() routine with a filter,
              FILT, defined as follows: 
                - FILT(r,c) == col_filter(r)*row_filter(c)
            - The intermediate filter computations will be carried out using variables of type EXP1::type.
              This is whatever scalar type is used inside the row_filter matrix. 
            - Pixel values are stored into out_img using the assign_pixel() function and therefore
              any applicable color space conversion or value saturation is performed.  Note that if 
              add_to is true then the filtered output value will be added to out_img rather than 
              overwriting the original value.
            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
                - The filter is applied to each color channel independently.
            - if (use_abs == true) then
                - pixel values after filtering that are < 0 are converted to their absolute values
            - The filter is applied such that it's centered over the pixel it writes its
              output into.  For centering purposes, we consider the center element of the
              filter to be FILT(col_filter.size()/2,row_filter.size()/2).  This means that
              the filter that writes its output to a pixel at location point(c,r) and is W
              by H (width by height) pixels in size operates on exactly the pixels in the
              rectangle centered_rect(point(c,r),W,H) within in_img.
            - Pixels close enough to the edge of in_img to not have the filter still fit 
              inside the image are always set to zero.
            - #out_img.nc() == in_img.nc()
            - #out_img.nr() == in_img.nr()
            - returns a rectangle which indicates what pixels in #out_img are considered 
              non-border pixels and therefore contain output from the filter.
            - if (use_abs == false && all images and filers contain float types) then
                - This function will use SIMD instructions and is particularly fast.  So if
                  you can use this form of the function it can give a decent speed boost.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename in_image_type,
        typename out_image_type,
        typename EXP1,
        typename EXP2
        >
    rectangle float_spatially_filter_image_separable (
        const in_image_type& in_img,
        out_image_type& out_img,
        const matrix_exp<EXP1>& row_filter,
        const matrix_exp<EXP2>& col_filter,
        out_image_type& scratch,
        bool add_to = false
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - in_img, out_img, row_filter, and col_filter must all contain float type elements.
            - is_same_object(in_img, out_img) == false 
            - row_filter.size() != 0
            - col_filter.size() != 0
            - is_vector(row_filter) == true
            - is_vector(col_filter) == true
        ensures
            - This function is identical to the above spatially_filter_image_separable()
              function except that it can only be invoked on float images with float
              filters.  In fact, spatially_filter_image_separable() invokes
              float_spatially_filter_image_separable() in those cases.  So why is
              float_spatially_filter_image_separable() in the public API?  The reason is
              because the separable filtering routines internally allocate an image each
              time they are called.  If you want to avoid this memory allocation then you
              can call float_spatially_filter_image_separable() and provide the scratch
              image as input.  This allows you to reuse the same scratch image for many
              calls to float_spatially_filter_image_separable() and thereby avoid having it
              allocated and freed for each call.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename in_image_type,
        typename out_image_type,
        typename EXP1,
        typename EXP2,
        typename T
        >
    rectangle spatially_filter_image_separable_down (
        const unsigned long downsample,
        const in_image_type& in_img,
        out_image_type& out_img,
        const matrix_exp<EXP1>& row_filter,
        const matrix_exp<EXP2>& col_filter,
        T scale = 1,
        bool use_abs = false,
        bool add_to = false
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type>::has_alpha == false
            - pixel_traits<typename out_image_type::type>::has_alpha == false 
            - pixel_traits<typename out_image_type::type>::grayscale == true 
            - is_same_object(in_img, out_img) == false 
            - T must be some scalar type
            - scale != 0
            - is_vector(row_filter) == true
            - is_vector(col_filter) == true
            - row_filter.size() % 2 == 1  (i.e. must be odd)
            - col_filter.size() % 2 == 1  (i.e. must be odd)
            - downsample > 0
        ensures
            - This function is equivalent to calling 
              spatially_filter_image_separable(in_img,out_img,row_filter,col_filter,scale,use_abs,add_to)
              and then downsampling the output image by a factor of downsample.  Therefore, 
              we will have that:
                - #out_img.nr() == ceil((double)in_img.nr()/downsample)
                - #out_img.nc() == ceil((double)in_img.nc()/downsample)
                - #out_img[r][c] == filtered pixel corresponding to in_img[r*downsample][c*downsample]
            - returns a rectangle which indicates what pixels in #out_img are considered 
              non-border pixels and therefore contain output from the filter.
            - Note that the first row and column of non-zero padded data are the following
                - first_row == ceil(floor(col_filter.size()/2.0)/downsample)
                - first_col == ceil(floor(row_filter.size()/2.0)/downsample)
    !*/

// ----------------------------------------------------------------------------------------

    template <
        long NR,
        long NC,
        typename T,
        typename U,
        typename in_image_type
        >
    inline void separable_3x3_filter_block_grayscale (
        T (&block)[NR][NC],
        const in_image_type& img,
        const long& r,
        const long& c,
        const U& fe1, 
        const U& fm,  
        const U& fe2 
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type> must be defined 
            - T and U should be scalar types
            - shrink_rect(get_rect(img),1).contains(c,r)
            - shrink_rect(get_rect(img),1).contains(c+NC-1,r+NR-1)
        ensures
            - Filters the image in the sub-window of img defined by a rectangle 
              with its upper left corner at (c,r) and lower right at (c+NC-1,r+NR-1).
            - The output of the filter is stored in #block.  Note that img will be 
              interpreted as a grayscale image.
            - The filter used is defined by the separable filter [fe1 fm fe2].  So the
              spatial filter is thus:
                fe1*fe1  fe1*fm  fe2*fe1
                fe1*fm   fm*fm   fe2*fm
                fe1*fe2  fe2*fm  fe2*fe2
    !*/

// ----------------------------------------------------------------------------------------

    template <
        long NR,
        long NC,
        typename T,
        typename U,
        typename in_image_type
        >
    inline void separable_3x3_filter_block_rgb (
        T (&block)[NR][NC],
        const in_image_type& img,
        const long& r,
        const long& c,
        const U& fe1, 
        const U& fm, 
        const U& fe2
    );
    /*!
        requires
            - in_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type>::rgb == true
            - T should be a struct with .red .green and .blue members.
            - U should be a scalar type
            - shrink_rect(get_rect(img),1).contains(c,r)
            - shrink_rect(get_rect(img),1).contains(c+NC-1,r+NR-1)
        ensures
            - Filters the image in the sub-window of img defined by a rectangle 
              with its upper left corner at (c,r) and lower right at (c+NC-1,r+NR-1).
            - The output of the filter is stored in #block.  Note that the filter is applied
              to each color component independently.
            - The filter used is defined by the separable filter [fe1 fm fe2].  So the
              spatial filter is thus:
                fe1*fe1  fe1*fm  fe2*fe1
                fe1*fm   fm*fm   fe2*fm
                fe1*fe2  fe2*fm  fe2*fe2
    !*/

// ----------------------------------------------------------------------------------------

    inline double gaussian (
        double x, 
        double sigma
    );
    /*!
        requires
            - sigma > 0
        ensures
            - computes and returns the value of a 1D Gaussian function with mean 0 
              and standard deviation sigma at the given x value.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename T
        >
    matrix<T,0,1> create_gaussian_filter (
        double sigma,
        int size 
    );
    /*!
        requires
            - sigma > 0
            - size > 0 
            - size is an odd number
        ensures
            - returns a separable Gaussian filter F such that:
                - is_vector(F) == true 
                - F.size() == size 
                - F is suitable for use with the spatially_filter_image_separable() routine
                  and its use with this function corresponds to running a Gaussian filter 
                  of sigma width over an image.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename in_image_type,
        typename out_image_type
        >
    void gaussian_blur (
        const in_image_type& in_img,
        out_image_type& out_img,
        double sigma = 1,
        int max_size = 1001
    );
    /*!
        requires
            - in_image_type  == is an implementation of array2d/array2d_kernel_abstract.h
            - out_image_type == is an implementation of array2d/array2d_kernel_abstract.h
            - pixel_traits<typename in_image_type::type>::has_alpha == false
            - pixel_traits<typename out_image_type::type>::has_alpha == false 
            - is_same_object(in_img, out_img) == false 
            - sigma > 0
            - max_size > 0
            - max_size is an odd number
        ensures
            - Filters in_img with a Gaussian filter of sigma width.  The actual spatial filter will
              be applied to pixel blocks that are at most max_size wide and max_size tall (note that
              this function will automatically select a smaller block size as appropriate).  The 
              results are stored into #out_img.
            - Pixel values are stored into out_img using the assign_pixel() function and therefore
              any applicable color space conversion or value saturation is performed.
            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
                - The filter is applied to each color channel independently.
            - Pixels close enough to the edge of in_img to not have the filter still fit 
              inside the image are set to zero.
            - #out_img.nc() == in_img.nc()
            - #out_img.nr() == in_img.nr()
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename image_type1, 
        typename image_type2
        >
    void sum_filter (
        const image_type1& img,
        image_type2& out,
        const rectangle& rect
    );
    /*!
        requires
            - out.nr() == img.nr() 
            - out.nc() == img.nc()
            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - is_same_object(img,out) == false
        ensures
            - for all valid r and c:
                - let SUM(r,c) == sum of pixels from img which are inside the rectangle 
                  translate_rect(rect, point(c,r)).
                - #out[r][c] == out[r][c] + SUM(r,c)
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename image_type1, 
        typename image_type2
        >
    void sum_filter_assign (
        const image_type1& img,
        image_type2& out,
        const rectangle& rect
    );
    /*!
        requires
            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - is_same_object(img,out) == false
        ensures
            - #out.nr() == img.nr() 
            - #out.nc() == img.nc()
            - for all valid r and c:
                - let SUM(r,c) == sum of pixels from img which are inside the rectangle 
                  translate_rect(rect, point(c,r)).
                - #out[r][c] == SUM(r,c)
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename image_type1, 
        typename image_type2
        >
    void max_filter (
        image_type1& img,
        image_type2& out,
        const long width,
        const long height,
        const typename image_type1::type& thresh
    );
    /*!
        requires
            - out.nr() == img.nr() 
            - out.nc() == img.nc()
            - image_type1 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - image_type2 == an implementation of array2d/array2d_kernel_abstract.h
              and it must contain a scalar type
            - is_same_object(img,out) == false
            - width > 0 && height > 0
        ensures
            - for all valid r and c:
                - let MAX(r,c) == maximum of pixels from img which are inside the rectangle 
                  centered_rect(point(c,r), width, height)
                - if (MAX(r,c) >= thresh)
                    - #out[r][c] == out[r][c] + MAX(r,c)
                - else
                    - #out[r][c] == out[r][c] + thresh 
            - Does not change the size of img.
            - Uses img as scratch space.  Therefore, the pixel values in img will have
              been modified by this function.  That is, max_filter() destroys the contents
              of img. 
    !*/

// ----------------------------------------------------------------------------------------

}

#endif // DLIB_SPATIAL_FILTERINg_ABSTRACT_

