/*
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* Copyright 2007 ZXing authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import NotFoundException from '../NotFoundException';
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/**
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* Implementations of this class can, given locations of finder patterns for a QR code in an
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* image, sample the right points in the image to reconstruct the QR code, accounting for
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* perspective distortion. It is abstracted since it is relatively expensive and should be allowed
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* to take advantage of platform-specific optimized implementations, like Sun's Java Advanced
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* Imaging library, but which may not be available in other environments such as J2ME, and vice
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* versa.
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*
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* The implementation used can be controlled by calling {@link #setGridSampler(GridSampler)}
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* with an instance of a class which implements this interface.
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*
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* @author Sean Owen
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*/
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class GridSampler {
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/**
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* <p>Checks a set of points that have been transformed to sample points on an image against
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* the image's dimensions to see if the point are even within the image.</p>
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*
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* <p>This method will actually "nudge" the endpoints back onto the image if they are found to be
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* barely (less than 1 pixel) off the image. This accounts for imperfect detection of finder
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* patterns in an image where the QR Code runs all the way to the image border.</p>
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*
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* <p>For efficiency, the method will check points from either end of the line until one is found
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* to be within the image. Because the set of points are assumed to be linear, this is valid.</p>
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*
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* @param image image into which the points should map
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* @param points actual points in x1,y1,...,xn,yn form
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* @throws NotFoundException if an endpoint is lies outside the image boundaries
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*/
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static checkAndNudgePoints(image, points) {
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const width = image.getWidth();
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const height = image.getHeight();
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// Check and nudge points from start until we see some that are OK:
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let nudged = true;
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for (let offset = 0; offset < points.length && nudged; offset += 2) {
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const x = Math.floor(points[offset]);
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const y = Math.floor(points[offset + 1]);
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if (x < -1 || x > width || y < -1 || y > height) {
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throw new NotFoundException();
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}
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nudged = false;
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if (x === -1) {
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points[offset] = 0.0;
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nudged = true;
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}
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else if (x === width) {
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points[offset] = width - 1;
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nudged = true;
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}
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if (y === -1) {
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points[offset + 1] = 0.0;
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nudged = true;
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}
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else if (y === height) {
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points[offset + 1] = height - 1;
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nudged = true;
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}
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}
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// Check and nudge points from end:
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nudged = true;
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for (let offset = points.length - 2; offset >= 0 && nudged; offset -= 2) {
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const x = Math.floor(points[offset]);
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const y = Math.floor(points[offset + 1]);
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if (x < -1 || x > width || y < -1 || y > height) {
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throw new NotFoundException();
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}
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nudged = false;
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if (x === -1) {
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points[offset] = 0.0;
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nudged = true;
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}
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else if (x === width) {
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points[offset] = width - 1;
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nudged = true;
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}
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if (y === -1) {
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points[offset + 1] = 0.0;
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nudged = true;
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}
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else if (y === height) {
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points[offset + 1] = height - 1;
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nudged = true;
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}
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}
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}
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}
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export default GridSampler;
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