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Added the max_filter() routine.
This commit is contained in:
Davis King
parent
c1c8267ba5
commit
fce8eaabe4
@ -715,6 +715,189 @@ namespace dlib
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}
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}
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// ----------------------------------------------------------------------------------------
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namespace impl
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{
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template <typename T>
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class fast_deque
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{
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/*
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This is a fast and minimal implementation of std::deque for
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use with the max_filter.
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This object assumes that no more than max_size elements
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will ever be pushed into it at a time.
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*/
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public:
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explicit fast_deque(unsigned long max_size)
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{
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// find a power of two that upper bounds max_size
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mask = 2;
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while (mask < max_size)
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mask *= 2;
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clear();
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data.resize(mask);
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--mask; // make into bit mask
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}
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void clear()
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{
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first = 1;
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last = 0;
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size = 0;
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}
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bool empty() const
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{
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return size == 0;
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}
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void pop_back()
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{
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last = (last-1)&mask;
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--size;
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}
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void push_back(const T& item)
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{
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last = (last+1)&mask;
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++size;
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data[last] = item;
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}
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void pop_front()
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{
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first = (first+1)&mask;
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--size;
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}
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const T& front() const
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{
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return data[first];
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}
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const T& back() const
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{
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return data[last];
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}
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private:
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std::vector<T> data;
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unsigned long mask;
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unsigned long first;
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unsigned long last;
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unsigned long size;
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};
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}
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// ----------------------------------------------------------------------------------------
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template <
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typename image_type1,
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typename image_type2
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>
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void max_filter (
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image_type1& img,
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image_type2& out,
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const long width,
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const long height,
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const typename image_type1::type& thresh
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)
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{
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DLIB_ASSERT((width%2)==1 &&
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(height%2)==1 &&
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width > 0 &&
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height > 0 &&
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out.nr() == img.nr() &&
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out.nc() == img.nc() &&
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is_same_object(img,out) == false,
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"\t void max_filter()"
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<< "\n\t Invalid arguments given to this function."
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<< "\n\t img.nr(): " << img.nr()
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<< "\n\t img.nc(): " << img.nc()
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<< "\n\t out.nr(): " << out.nr()
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<< "\n\t out.nc(): " << out.nc()
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<< "\n\t width: " << width
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<< "\n\t height: " << height
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<< "\n\t is_same_object(img,out): " << is_same_object(img,out)
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);
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typedef typename image_type1::type pixel_type;
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dlib::impl::fast_deque<std::pair<long,pixel_type> > Q(std::max(width,height));
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const long last_col = std::max(img.nc(), (width/2));
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const long last_row = std::max(img.nr(), (height/2));
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// run max filter along rows of img
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for (long r = 0; r < img.nr(); ++r)
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{
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Q.clear();
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for (long c = 0; c < width/2 && c < img.nc(); ++c)
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{
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while (!Q.empty() && img[r][c] >= Q.back().second)
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Q.pop_back();
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Q.push_back(make_pair(c,img[r][c]));
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}
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for (long c = width/2; c < img.nc(); ++c)
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{
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while (!Q.empty() && img[r][c] >= Q.back().second)
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Q.pop_back();
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while (!Q.empty() && Q.front().first <= c-width)
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Q.pop_front();
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Q.push_back(make_pair(c,img[r][c]));
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img[r][c-(width/2)] = Q.front().second;
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}
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for (long c = last_col; c < img.nc() + (width/2); ++c)
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{
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while (!Q.empty() && Q.front().first <= c-width)
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Q.pop_front();
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img[r][c-(width/2)] = Q.front().second;
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}
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}
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// run max filter along columns of img. Store result in out.
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for (long cc = 0; cc < img.nc(); ++cc)
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{
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Q.clear();
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for (long rr = 0; rr < height/2 && rr < img.nr(); ++rr)
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{
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while (!Q.empty() && img[rr][cc] >= Q.back().second)
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Q.pop_back();
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Q.push_back(make_pair(rr,img[rr][cc]));
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}
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for (long rr = height/2; rr < img.nr(); ++rr)
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{
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while (!Q.empty() && img[rr][cc] >= Q.back().second)
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Q.pop_back();
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while (!Q.empty() && Q.front().first <= rr-height)
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Q.pop_front();
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Q.push_back(make_pair(rr,img[rr][cc]));
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out[rr-(height/2)][cc] += std::max(Q.front().second, thresh);
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}
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for (long rr = last_row; rr < img.nr() + (height/2); ++rr)
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{
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while (!Q.empty() && Q.front().first <= rr-height)
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Q.pop_front();
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out[rr-(height/2)][cc] += std::max(Q.front().second, thresh);
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}
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}
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}
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// ----------------------------------------------------------------------------------------
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}
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@ -338,6 +338,45 @@ namespace dlib
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- #out[r][c] == out[r][c] + SUM(r,c)
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!*/
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// ----------------------------------------------------------------------------------------
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template <
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typename image_type1,
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typename image_type2
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>
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void max_filter (
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image_type1& img,
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image_type2& out,
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const long width,
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const long height,
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const typename image_type1::type& thresh
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);
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/*!
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requires
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- out.nr() == img.nr()
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- out.nc() == img.nc()
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- image_type1 == an implementation of array2d/array2d_kernel_abstract.h
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and it must contain a scalar type
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- image_type2 == an implementation of array2d/array2d_kernel_abstract.h
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and it must contain a scalar type
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- is_same_object(img,out) == false
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- (width%2)==1 && (height%2)==1
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(i.e. width and height must be odd)
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- width > 0 && height > 0
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ensures
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- for all valid r and c:
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- let MAX(r,c) == maximum of pixels from img which are inside the rectangle
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centered_rect(point(c,r), width, height)
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- if (MAX(r,c) >= thresh)
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- #out[r][c] == out[r][c] + MAX(r,c)
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- else
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- #out[r][c] == out[r][c] + thresh
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- Does not change the size of img.
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- Uses img as scratch space. Therefore, the pixel values in img will have
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been modified by this function. That is, max_filter() destroys the contents
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of img.
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!*/
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// ----------------------------------------------------------------------------------------
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}
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@ -440,6 +440,105 @@ namespace
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}
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}
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// ----------------------------------------------------------------------------------------
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template <
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typename image_type1,
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typename image_type2
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>
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void naive_max_filter (
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const image_type1& img,
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image_type2& out,
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const rectangle& rect,
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typename image_type1::type thresh
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)
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{
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typedef typename image_type1::type pixel_type;
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const rectangle area = get_rect(img);
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for (long r = 0; r < img.nr(); ++r)
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{
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for (long c = 0; c < img.nc(); ++c)
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{
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const rectangle win = translate_rect(rect,point(c,r)).intersect(area);
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if (!win.is_empty())
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out[r][c] += std::max(dlib::max(subm(array_to_matrix(img),win)), thresh);
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else
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out[r][c] += thresh;
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}
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}
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}
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// ----------------------------------------------------------------------------------------
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void test_max_filter(long rows, long cols, long width, long height, dlib::rand& rnd)
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{
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array2d<int> img(rows, cols);
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rectangle rect = centered_rect(0,0, width, height);
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array2d<int> out(img.nr(),img.nc());
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assign_all_pixels(out, 0);
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array2d<int> out2(img.nr(),img.nc());
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assign_all_pixels(out2, 0);
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for (long r = 0; r < img.nr(); ++r)
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{
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for (long c = 0; c < img.nc(); ++c)
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{
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img[r][c] = rnd.get_random_32bit_number();
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}
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}
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const int thresh = rnd.get_random_32bit_number();
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naive_max_filter(img, out2, rect, thresh);
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max_filter(img, out, rect.width(), rect.height(), thresh);
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DLIB_TEST_MSG(array_to_matrix(out) == array_to_matrix(out2),
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"rows: "<< rows
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<< "\ncols: "<< rows
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<< "\nwidth: "<< width
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<< "\nheight: "<< height );
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}
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// ----------------------------------------------------------------------------------------
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void test_max_filter()
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{
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dlib::rand rnd;
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for (int iter = 0; iter < 300; ++iter)
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{
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print_spinner();
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test_max_filter(0,0,1,1,rnd);
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test_max_filter(0,0,3,1,rnd);
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test_max_filter(0,0,3,3,rnd);
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test_max_filter(0,0,1,3,rnd);
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test_max_filter(1,1,1,1,rnd);
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test_max_filter(2,2,1,1,rnd);
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test_max_filter(3,3,1,1,rnd);
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test_max_filter(3,3,3,3,rnd);
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test_max_filter(3,3,3,5,rnd);
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test_max_filter(20,20,901,901,rnd);
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test_max_filter(5,5,1,5,rnd);
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test_max_filter(50,50,9,9,rnd);
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test_max_filter(50,50,9,9,rnd);
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test_max_filter(50,50,9,9,rnd);
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test_max_filter(20,20,1,901,rnd);
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test_max_filter(20,20,3,901,rnd);
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test_max_filter(20,20,901,1,rnd);
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}
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for (int iter = 0; iter < 200; ++iter)
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{
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print_spinner();
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test_max_filter((int)rnd.get_random_8bit_number()%100+1,
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(int)rnd.get_random_8bit_number()%100+1,
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(int)rnd.get_random_8bit_number()*2+1,
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(int)rnd.get_random_8bit_number()*2+1,
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rnd);
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}
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}
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// ----------------------------------------------------------------------------------------
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class scan_image_tester : public tester
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@ -454,6 +553,8 @@ namespace
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void perform_test (
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)
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{
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test_max_filter();
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run_test1();
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run_test2();
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run_test3<unsigned char>(1);
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