| 1 | // |
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| 2 | // Copyright 2005-2007 Adobe Systems Incorporated |
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| 3 | // |
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| 4 | // Distributed under the Boost Software License, Version 1.0 |
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| 5 | // See accompanying file LICENSE_1_0.txt or copy at |
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| 6 | // http://www.boost.org/LICENSE_1_0.txt |
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| 7 | // |
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| 8 | |
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| 9 | #include <boost/gil/extension/io/jpeg.hpp> |
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| 10 | |
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| 11 | // Demonstrates how to compute gradients along the x-axis |
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| 12 | // This example converts the input image to a greyscale view via color_converted_view, |
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| 13 | // and then relies on the function static_transform to apply the operation halfdiff_cast_channels. |
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| 14 | // The result is captured in a view, initially blacked out via a call to fill_pixels (defined in |
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| 15 | // include/boost/gil/algorithm.hpp) |
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| 16 | // static_transform is defined in include/boost/gil/color_based_algorithm.hpp and applies an operation |
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| 17 | // to either a single source or two sources and a destination (as is the case here). |
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| 18 | // In this example, the gradient is calculated as half the difference between the two pixels surrounding x |
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| 19 | // in the loop in x_gradient. |
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| 20 | |
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| 21 | using namespace boost::gil; |
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| 22 | |
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| 23 | template <typename Out> |
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| 24 | struct halfdiff_cast_channels { |
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| 25 | template <typename T> Out operator()(const T& in1, const T& in2) const { |
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| 26 | return Out((in2-in1)/2); |
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| 27 | } |
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| 28 | }; |
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| 29 | |
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| 30 | |
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| 31 | template <typename SrcView, typename DstView> |
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| 32 | void x_gradient(SrcView const& src, DstView const& dst) |
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| 33 | { |
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| 34 | using dst_channel_t = typename channel_type<DstView>::type; |
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| 35 | |
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| 36 | for (int y = 0; y < src.height(); ++y) |
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| 37 | { |
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| 38 | typename SrcView::x_iterator src_it = src.row_begin(y); |
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| 39 | typename DstView::x_iterator dst_it = dst.row_begin(y); |
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| 40 | |
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| 41 | for (int x = 1; x < src.width() - 1; ++x) |
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| 42 | { |
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| 43 | static_transform(src_it[x - 1], src_it[x + 1], dst_it[x], |
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| 44 | halfdiff_cast_channels<dst_channel_t>()); |
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| 45 | } |
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| 46 | } |
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| 47 | } |
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| 48 | |
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| 49 | template <typename SrcView, typename DstView> |
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| 50 | void x_luminosity_gradient(SrcView const& src, DstView const& dst) |
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| 51 | { |
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| 52 | using gray_pixel_t = pixel<typename channel_type<SrcView>::type, gray_layout_t>; |
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| 53 | x_gradient(color_converted_view<gray_pixel_t>(src), dst); |
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| 54 | } |
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| 55 | |
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| 56 | int main() |
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| 57 | { |
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| 58 | rgb8_image_t img; |
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| 59 | read_image(file_name: "test.jpg" ,img, tag: jpeg_tag{}); |
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| 60 | |
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| 61 | gray8s_image_t img_out(img.dimensions()); |
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| 62 | fill_pixels(view: view(img&: img_out),value: int8_t(0)); |
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| 63 | |
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| 64 | x_luminosity_gradient(src: const_view(img), dst: view(img&: img_out)); |
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| 65 | write_view(file_name: "out-x_gradient.jpg" ,view: color_converted_view<gray8_pixel_t>(src: const_view(img: img_out)), tag: jpeg_tag{}); |
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| 66 | |
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| 67 | return 0; |
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| 68 | } |
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| 69 | |
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