zxing-js/library

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src/core/qrcode/encoder/MaskUtil.ts

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/*
 * Copyright 2008 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*namespace com.google.zxing.qrcode.encoder {*/

import ByteMatrix from './ByteMatrix';

import IllegalArgumentException from '../../IllegalArgumentException';

/**
 * @author Satoru Takabayashi
 * @author Daniel Switkin
 * @author Sean Owen
 */
export default class MaskUtil {

    // Penalty weights from section 6.8.2.1
    private static N1 = 3;
    private static N2 = 3;
    private static N3 = 40;
    private static N4 = 10;

    private constructor() {
        // do nothing
    }

    /**
     * Apply mask penalty rule 1 and return the penalty. Find repetitive cells with the same color and
     * give penalty to them. Example: 00000 or 11111.
     */
    public static applyMaskPenaltyRule1(matrix: ByteMatrix): number /*int*/ {
        return MaskUtil.applyMaskPenaltyRule1Internal(matrix, true) + MaskUtil.applyMaskPenaltyRule1Internal(matrix, false);
    }

    /**
     * Apply mask penalty rule 2 and return the penalty. Find 2x2 blocks with the same color and give
     * penalty to them. This is actually equivalent to the spec's rule, which is to find MxN blocks and give a
     * penalty proportional to (M-1)x(N-1), because this is the number of 2x2 blocks inside such a block.
     */
    public static applyMaskPenaltyRule2(matrix: ByteMatrix): number /*int*/ {
        let penalty = 0;
        const array: Array<Uint8Array> = matrix.getArray();
        const width: number /*int*/ = matrix.getWidth();
        const height: number /*int*/ = matrix.getHeight();
        for (let y = 0; y < height - 1; y++) {
            const arrayY = array[y];
            for (let x = 0; x < width - 1; x++) {
                const value = arrayY[x];
                if (value === arrayY[x + 1] && value === array[y + 1][x] && value === array[y + 1][x + 1]) {
                    penalty++;
                }
            }
        }
        return MaskUtil.N2 * penalty;
    }

    /**
     * Apply mask penalty rule 3 and return the penalty. Find consecutive runs of 1:1:3:1:1:4
     * starting with black, or 4:1:1:3:1:1 starting with white, and give penalty to them.  If we
     * find patterns like 000010111010000, we give penalty once.
     */
    public static applyMaskPenaltyRule3(matrix: ByteMatrix): number /*int*/ {
        let numPenalties = 0;
        const array: Array<Uint8Array> = matrix.getArray();
        const width: number /*int*/ = matrix.getWidth();
        const height: number /*int*/ = matrix.getHeight();
        for (let y = 0; y < height; y++) {
            for (let x = 0; x < width; x++) {
                const arrayY: Uint8Array = array[y];  // We can at least optimize this access
                if (x + 6 < width &&
                    arrayY[x] === 1 &&
                    arrayY[x + 1] === 0 &&
                    arrayY[x + 2] === 1 &&
                    arrayY[x + 3] === 1 &&
                    arrayY[x + 4] === 1 &&
                    arrayY[x + 5] === 0 &&
                    arrayY[x + 6] === 1 &&
                    (MaskUtil.isWhiteHorizontal(arrayY, x - 4, x) || MaskUtil.isWhiteHorizontal(arrayY, x + 7, x + 11))) {
                    numPenalties++;
                }
                if (y + 6 < height &&
                    array[y][x] === 1 &&
                    array[y + 1][x] === 0 &&
                    array[y + 2][x] === 1 &&
                    array[y + 3][x] === 1 &&
                    array[y + 4][x] === 1 &&
                    array[y + 5][x] === 0 &&
                    array[y + 6][x] === 1 &&
                    (MaskUtil.isWhiteVertical(array, x, y - 4, y) || MaskUtil.isWhiteVertical(array, x, y + 7, y + 11))) {
                    numPenalties++;
                }
            }
        }
        return numPenalties * MaskUtil.N3;
    }

    private static isWhiteHorizontal(rowArray: Uint8Array, from: number /*int*/, to: number /*int*/): boolean {
        from = Math.max(from, 0);
        to = Math.min(to, rowArray.length);
        for (let i = from; i < to; i++) {
            if (rowArray[i] === 1) {
                return false;
            }
        }
        return true;
    }

    private static isWhiteVertical(array: Uint8Array[], col: number /*int*/, from: number /*int*/, to: number /*int*/): boolean {
        from = Math.max(from, 0);
        to = Math.min(to, array.length);
        for (let i = from; i < to; i++) {
            if (array[i][col] === 1) {
                return false;
            }
        }
        return true;
    }

    /**
     * Apply mask penalty rule 4 and return the penalty. Calculate the ratio of dark cells and give
     * penalty if the ratio is far from 50%. It gives 10 penalty for 5% distance.
     */
    public static applyMaskPenaltyRule4(matrix: ByteMatrix): number /*int*/ {
        let numDarkCells = 0;
        const array: Array<Uint8Array> = matrix.getArray();
        const width: number /*int*/ = matrix.getWidth();
        const height: number /*int*/ = matrix.getHeight();
        for (let y = 0; y < height; y++) {
            const arrayY: Uint8Array = array[y];
            for (let x = 0; x < width; x++) {
                if (arrayY[x] === 1) {
                    numDarkCells++;
                }
            }
        }
        const numTotalCells = matrix.getHeight() * matrix.getWidth();
        const fivePercentVariances = Math.floor(Math.abs(numDarkCells * 2 - numTotalCells) * 10 / numTotalCells);
        return fivePercentVariances * MaskUtil.N4;
    }

    /**
     * Return the mask bit for "getMaskPattern" at "x" and "y". See 8.8 of JISX0510:2004 for mask
     * pattern conditions.
     */
    public static getDataMaskBit(maskPattern: number /*int*/, x: number /*int*/, y: number /*int*/): boolean {
        let intermediate: number; /*int*/
        let temp: number; /*int*/
        switch (maskPattern) {
            case 0:
                intermediate = (y + x) & 0x1;
                break;
            case 1:
                intermediate = y & 0x1;
                break;
            case 2:
                intermediate = x % 3;
                break;
            case 3:
                intermediate = (y + x) % 3;
                break;
            case 4:
                intermediate = (Math.floor(y / 2) + Math.floor(x / 3)) & 0x1;
                break;
            case 5:
                temp = y * x;
                intermediate = (temp & 0x1) + (temp % 3);
                break;
            case 6:
                temp = y * x;
                intermediate = ((temp & 0x1) + (temp % 3)) & 0x1;
                break;
            case 7:
                temp = y * x;
                intermediate = ((temp % 3) + ((y + x) & 0x1)) & 0x1;
                break;
            default:
                throw new IllegalArgumentException('Invalid mask pattern: ' + maskPattern);
        }
        return intermediate === 0;
    }

    /**
     * Helper function for applyMaskPenaltyRule1. We need this for doing this calculation in both
     * vertical and horizontal orders respectively.
     */
    private static applyMaskPenaltyRule1Internal(matrix: ByteMatrix, isHorizontal: boolean): number /*int*/ {
        let penalty = 0;
        const iLimit = isHorizontal ? matrix.getHeight() : matrix.getWidth();
        const jLimit = isHorizontal ? matrix.getWidth() : matrix.getHeight();
        const array: Array<Uint8Array> = matrix.getArray();
        for (let i = 0; i < iLimit; i++) {
            let numSameBitCells = 0;
            let prevBit = -1;
            for (let j = 0; j < jLimit; j++) {
                const bit = isHorizontal ? array[i][j] : array[j][i];
                if (bit === prevBit) {
                    numSameBitCells++;
                } else {
                    if (numSameBitCells >= 5) {
                        penalty += MaskUtil.N1 + (numSameBitCells - 5);
                    }
                    numSameBitCells = 1;  // Include the cell itself.
                    prevBit = bit;
                }
            }
            if (numSameBitCells >= 5) {
                penalty += MaskUtil.N1 + (numSameBitCells - 5);
            }
        }
        return penalty;
    }

}