90 lines
2.7 KiB
C++
90 lines
2.7 KiB
C++
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/*
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* Copyright 2016 Nu-book Inc.
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* Copyright 2016 ZXing authors
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* Copyright 2020 Axel Waggershauser
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*/
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// SPDX-License-Identifier: Apache-2.0
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#include "GridSampler.h"
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#ifdef PRINT_DEBUG
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#include "LogMatrix.h"
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#include "BitMatrixIO.h"
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#endif
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namespace ZXing {
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#ifdef PRINT_DEBUG
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LogMatrix log;
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#endif
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DetectorResult SampleGrid(const BitMatrix& image, int width, int height, const PerspectiveTransform& mod2Pix)
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{
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return SampleGrid(image, width, height, {ROI{0, width, 0, height, mod2Pix}});
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}
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DetectorResult SampleGrid(const BitMatrix& image, int width, int height, const ROIs& rois)
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{
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#ifdef PRINT_DEBUG
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LogMatrix log;
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static int i = 0;
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LogMatrixWriter lmw(log, image, 5, "grid" + std::to_string(i++) + ".pnm");
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#endif
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if (width <= 0 || height <= 0)
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return {};
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for (auto&& [x0, x1, y0, y1, mod2Pix] : rois) {
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// Precheck the corners of every roi to bail out early if the grid is "obviously" not completely inside the image
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auto isInside = [&mod2Pix = mod2Pix, &image](int x, int y) { return image.isIn(mod2Pix(centered(PointI(x, y)))); };
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if (!mod2Pix.isValid() || !isInside(x0, y0) || !isInside(x1 - 1, y0) || !isInside(x1 - 1, y1 - 1) || !isInside(x0, y1 - 1))
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return {};
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}
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BitMatrix res(width, height);
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for (auto&& [x0, x1, y0, y1, mod2Pix] : rois) {
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for (int y = y0; y < y1; ++y)
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for (int x = x0; x < x1; ++x) {
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auto p = mod2Pix(centered(PointI{x, y}));
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// Due to a "numerical instability" in the PerspectiveTransform generation/application it has been observed
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// that even though all boundary grid points get projected inside the image, it can still happen that an
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// inner grid points is not. See #563. A true perspective transformation cannot have this property.
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// The following check takes 100% care of the issue and turned out to be less of a performance impact than feared.
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// TODO: Check some mathematical/numercial property of mod2Pix to determine if it is a perspective transforation.
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if (!image.isIn(p))
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return {};
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#ifdef PRINT_DEBUG
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log(p, 3);
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#endif
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#if 0
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int sum = 0;
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for (int dy = -1; dy <= 1; ++dy)
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for (int dx = -1; dx <= 1; ++dx)
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sum += image.get(p + PointF(dx, dy));
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if (sum >= 5)
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#else
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if (image.get(p))
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#endif
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res.set(x, y);
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}
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}
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#ifdef PRINT_DEBUG
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printf("width: %d, height: %d\n", width, height);
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// printf("%s", ToString(res).c_str());
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#endif
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auto projectCorner = [&](PointI p) {
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for (auto&& [x0, x1, y0, y1, mod2Pix] : rois)
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if (x0 <= p.x && p.x <= x1 && y0 <= p.y && p.y <= y1)
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return PointI(mod2Pix(PointF(p)) + PointF(0.5, 0.5));
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return PointI();
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};
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return {std::move(res),
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{projectCorner({0, 0}), projectCorner({width, 0}), projectCorner({width, height}), projectCorner({0, height})}};
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}
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} // ZXing
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