Ensure all examples build without error

example/Jamfile

@@ -11,6 +11,7 @@ import regex ;
 import testing ;
 
 using libjpeg : : : : true ; # work around bug on master
+using libpng : : : : true ;
 
 project
     : # requirements
@@ -19,6 +20,7 @@ project
 # TODO: Add missing examples
 
 local sources =
+    adaptive_he.cpp
     adaptive_threshold.cpp
     affine.cpp
     anisotropic_diffusion.cpp
@@ -27,12 +29,18 @@ local sources =
     dynamic_image.cpp
     harris.cpp
     hessian.cpp
+    histogram_equalization.cpp
+    histogram_matching.cpp
     histogram.cpp
+    hough_transform_circle.cpp
+    hough_transform_line.cpp
     interleaved_ptr.cpp
     mandelbrot.cpp
     morphology.cpp
     packed_pixel.cpp
+    rasterizer_circle.cpp
     rasterizer_ellipse.cpp
+    rasterizer_line.cpp
     resize.cpp
     sobel_scharr.cpp
     threshold.cpp
@@ -44,11 +52,13 @@ local targets ;
 
 for local s in $(sources)
 {
-    targets +=
-        [ compile $(s) :
-            [ ac.check-library /libjpeg//libjpeg : <library>/libjpeg//libjpeg : <build>no ]
-        ]
-        ;
+targets +=
+    	[ exe [ regex.replace $(s)  ".cpp" "" ] :
+	    $(s)
+	    /libjpeg//libjpeg
+    	    /libpng//libpng
+	]
+	;
 }
 
 alias examples : $(targets) ;

example/adaptive_he.cpp

@@ -13,6 +13,13 @@
 
 using namespace boost::gil;
 
+// Demonstrates Adaptive Histogram Equalization (AHE)
+
+// See also:
+// histogram.cpp - General use of histograms in GIL
+// histogram_equalization.cpp - Regular Histogram Equalization
+// histogram_matching.cpp - Reference-based histogram computation
+
 int main()
 {
     gray8_image_t img;

example/adaptive_threshold.cpp

@@ -5,12 +5,22 @@
 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 //
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/io/png.hpp>
 #include <iostream>
 
 using namespace boost::gil;
 
+// Demonstrates Adaptive Thresholding
+
+// threshold_adaptive works following either the mean or the gaussian method, and accepts also a direction
+// The direction indicates whether the pixels are assigned the max value when their values are greater
+// than the threshold (regular), or when they are less than the threshold (inverse)
+// threshold_adaptive is defined in include/boost/gil/image_processing/threshold.hpp
+// See also:
+// threshold.cpp - Simple thresholding
+
 int main()
 {
     gray8_image_t img;

example/affine.cpp

@@ -5,12 +5,17 @@
 // See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt
 //
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/io/jpeg.hpp>
 #include <boost/gil/extension/numeric/sampler.hpp>
 #include <boost/gil/extension/numeric/resample.hpp>
 
-// Example for resample_pixels() in the numeric extension
+// Performs an arbitrary affine transformation on the image.
+
+// This example relies on the matrices and functions available in GIL to define the operation,
+// in include/boost/gil/extension/numeric/affine.hpp
+// and calls resample_pixels(), avaiable in the numeric extension, to apply it
 
 int main()
 {

example/anisotropic_diffusion.cpp

@@ -5,6 +5,7 @@
 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 //
+
 #include <boost/gil/algorithm.hpp>
 #include <boost/gil/extension/io/png.hpp>
 #include <boost/gil/image.hpp>
@@ -20,6 +21,12 @@
 
 namespace gil = boost::gil;
 
+// Demonstrates Anisotropic Diffusion
+
+// This example uses the Perona-Malik's diffusion algorithm, which is the default in GIL.
+// In addition, Gaussian conductivity and two wide range conductivity functions are also available.
+// see include/boost/gil/image_processing/diffusion.hpp
+
 void gray_version(std::string const& input_path, std::string const& output_path,
                   unsigned int iteration_count, float kappa)
 {

example/convolution.cpp

@@ -4,12 +4,24 @@
 // Distributed under the Boost Software License, Version 1.0
 // See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/io/jpeg.hpp>
 #include <boost/gil/extension/numeric/kernel.hpp>
 #include <boost/gil/extension/numeric/convolve.hpp>
 
-// Example for convolve_rows() and convolve_cols() in the numeric extension
+// Convolves the image with a Gaussian kernel.
+
+// Note that the kernel can be fixed or resizable:
+// kernel_1d_fixed<float, N> k(matrix, centre) produces a fixed kernel
+// kernel_1d<float> k(matrix, size, centre) produces a resizable kernel
+
+// Work can be done row by row and column by column, as in this example,
+// using the functions convolve_rows and convolve_cols (or their _fixed counterpart)
+// but the header boost/gil/extension/numeric/convolve.hpp also offers the function convolve_1d which combines the two.
+
+// See also:
+// convolve2d.cpp - Convolution with 2d kernels
 
 int main() {
     using namespace boost::gil;

example/convolve2d.cpp

@@ -1,12 +1,33 @@
+// 
+// Copyright 2005-2007 Adobe Systems Incorporated 
+// 
+// Distributed under the Boost Software License, Version 1.0 
+// See accompanying file LICENSE_1_0.txt or copy at 
+// http://www.boost.org/LICENSE_1_0.txt 
+// 
+
 #include <vector>
 #include <iostream>
 #include <boost/gil/extension/numeric/kernel.hpp>
 #include <boost/gil/extension/numeric/convolve.hpp>
 #include <boost/gil/extension/io/png.hpp>
 
 #include <boost/gil/extension/io/jpeg.hpp>
+
 using namespace boost::gil;
 using namespace std;
+
+// Convolves the image with a 2d kernel.
+
+// Note that the kernel can be fixed or resizable:
+// kernel_2d_fixed<float, N> k(elements, centre_y, centre_x) produces a fixed kernel
+// kernel_2d<float> k(elements, size, centre_y, centre_x) produces a resizable kernel
+// The size of the kernel matrix is deduced as the square root of the number of the elements (9 elements yield a 3x3 matrix)
+
+// See also:
+// convolution.cpp - Convolution with 2d kernels
+
+
 int main()
 {
     //gray8_image_t img;

example/dynamic_image.cpp

@@ -5,18 +5,23 @@
 // See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt
 //
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/dynamic_image/any_image.hpp>
 #include <boost/gil/extension/io/jpeg.hpp>
 #include <boost/mp11.hpp>
 
+// Demonstrates how to use images whose type is instantiated at run time.
+
 int main()
 {
     namespace gil = boost::gil;
 
     gil::any_image<gil::gray8_image_t, gil::rgb8_image_t, gil::gray16_image_t, gil::rgb16_image_t> dynamic_image;
     gil::read_image("test.jpg", dynamic_image, gil::jpeg_tag());
+
     // Save the image upside down, preserving its native color space and channel depth
     auto view = gil::flipped_up_down_view(gil::const_view(dynamic_image));
+
     gil::write_view("out-dynamic_image.jpg", view, gil::jpeg_tag());
 }

example/harris.cpp

@@ -5,6 +5,7 @@
 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 //
+
 #include <boost/gil/extension/io/png.hpp>
 #include <boost/gil/extension/numeric/convolve.hpp>
 #include <boost/gil/image.hpp>
@@ -23,6 +24,8 @@
 
 namespace gil = boost::gil;
 
+// Demonstrates Harris corner detection
+
 // some images might produce artifacts
 // when converted to grayscale,
 // which was previously observed on
@@ -157,11 +160,11 @@ int main(int argc, char* argv[])
 
     gil::rgb8_image_t input_image;
 
-    gil::read_image(argv[1], input_image, gil::png_tag{});
+    gil::read_image(argv[1], input_image, gil::png_tag{}); 
     auto original_image = input_image;
     auto original_view = gil::view(original_image);
     auto input_view = gil::view(input_image);
-    auto grayscaled = to_grayscale(input_view);
+    auto grayscaled = to_grayscale(input_view); 
     gil::gray8_image_t smoothed_image(grayscaled.dimensions());
     auto smoothed = gil::view(smoothed_image);
     apply_gaussian_blur(gil::view(grayscaled), smoothed);

example/hessian.cpp

@@ -1,3 +1,11 @@
+// 
+// Copyright 2005-2007 Adobe Systems Incorporated 
+// 
+// Distributed under the Boost Software License, Version 1.0 
+// See accompanying file LICENSE_1_0.txt or copy at 
+// http://www.boost.org/LICENSE_1_0.txt 
+//
+
 #include <boost/gil/image.hpp>
 #include <boost/gil/image_view.hpp>
 #include <boost/gil/image_processing/numeric.hpp>
@@ -11,6 +19,8 @@
 
 namespace gil = boost::gil;
 
+// Demonstrates Hessian feature (blob) detection
+
 // some images might produce artifacts
 // when converted to grayscale,
 // which was previously observed on

example/histogram.cpp

@@ -14,10 +14,13 @@
 
 using namespace boost::gil;
 
-/*
-This file explains how to use the histogram class and some of its features
-that can be applied for a variety of tasks.
-*/
+// Explains how to use the histogram class and some of its features
+// that can be applied for a variety of tasks.
+
+// See also:
+// histogram_equalization.cpp - Regular Histogram Equalization
+// adaptive_he.cpp - Adaptive Histogram Equalization
+// histogram_matching.cpp - Reference-based histogram computation
 
 int main()
 {
@@ -34,7 +37,7 @@ int main()
         h,       // Histogram to be filled
         1,       // Histogram bin widths
         false,   // Specify whether to accumulate over the values already present in h (default = false)
-        true,    // Specify whether to have a sparse or continuous histogram (default = true)
+        true,    // Specify whether to have a sparse (true) or continuous histogram (false) (default = true)
         false,   // Specify if image mask is to be specified
         {{}},    // Mask as a 2D vector. Used only if prev argument specified
         {0},     // Lower limit on the values in histogram (default numeric_limit::min() on axes)

example/histogram_equalization.cpp

@@ -1,9 +1,24 @@
+// 
+// Copyright 2005-2007 Adobe Systems Incorporated 
+// 
+// Distributed under the Boost Software License, Version 1.0 
+// See accompanying file LICENSE_1_0.txt or copy at 
+// http://www.boost.org/LICENSE_1_0.txt 
+// 
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/io/png.hpp>
 #include <boost/gil/image_processing/histogram_equalization.hpp>
 
 using namespace boost::gil;
 
+// Demonstrates Histogram Equalization
+
+// See also:
+// histogram.cpp - General use of histograms in GIL
+// adaptive_he.cpp - Adaptive Histogram Equalization
+// histogram_matching.cpp - Reference-based histogram computation
+
 int main()
 {
     gray8_image_t img;

example/histogram_matching.cpp

@@ -14,6 +14,13 @@
 
 using namespace boost::gil;
 
+// Demonstrates Histogram Matching
+
+// See also:
+// histogram_equalization.cpp - Regular Histogram Equalization
+// adaptive_he.cpp - Adaptive Histogram Equalization
+// histogram.cpp - General use of histograms in GIL
+
 std::vector<std::vector<bool>> get_mask(gray8_view_t const& mask)
 {
     std::vector<std::vector<bool>> mask_vec(mask.height(), std::vector<bool>(mask.width(), 0));

example/hough_transform_circle.cpp

@@ -1,11 +1,11 @@
-// Boost.GIL (Generic Image Library) - tests
 //
 // Copyright 2020 Olzhas Zhumabek <[email protected]>
 //
 // Use, modification and distribution are subject to the Boost Software License,
 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 //
+
 #include <boost/gil.hpp>
 #include <boost/gil/extension/io/png.hpp>
 
@@ -15,6 +15,16 @@
 
 namespace gil = boost::gil;
 
+// Demonstrates how to use a Hough transform to identify a circle
+
+// Note this relies on the brute force approach, which today is the only one available in GIL
+// The function hough_circle_transform_brute, defined in include/boost/gil/image_processing/hough_transform.cpp,
+// accepts a greyscale edge map, the three Hough parameters allowing to do the drawing and the voting,
+// an accumulator in the form of an iterator of views of the parameter space and a utility rasterizer to produce the points.
+// The example outputs the voting cell of the centre of a circle drawn programatically.
+// See also:
+// hough_transform_line.cpp - Hough transform to detect lines
+
 int main()
 {
     const std::size_t size = 128;