Package com.google.zxing.pdf417.detector

Class Detector

  • public final class Detector
extends java.lang.Object

    Encapsulates logic that can detect a PDF417 Code in an image, even if the PDF417 Code is rotated or skewed, or partially obscured.

    • Field Detail

      • INDEXES_START_PATTERN

        private static final int[] INDEXES_START_PATTERN

      • INDEXES_STOP_PATTERN

        private static final int[] INDEXES_STOP_PATTERN

      • MAX_INDIVIDUAL_VARIANCE

        private static final float MAX_INDIVIDUAL_VARIANCE
        See Also:
        Constant Field Values

      • MAX_STOP_PATTERN_HEIGHT_VARIANCE

        private static final float MAX_STOP_PATTERN_HEIGHT_VARIANCE
        See Also:
        Constant Field Values

      • START_PATTERN

        private static final int[] START_PATTERN

      • STOP_PATTERN

        private static final int[] STOP_PATTERN

      • ROTATIONS

        private static final int[] ROTATIONS

    • Constructor Detail

      • Detector

        private Detector()

    • Method Detail

      • detect

        public static PDF417DetectorResult detect​(BinaryBitmap image,
                                          java.util.Map<DecodeHintType,​?> hints,
                                          boolean multiple)
                                   throws NotFoundException

        Detects a PDF417 Code in an image. Checks 0, 90, 180, and 270 degree rotations.

        Parameters:
        image - barcode image to decode
        hints - optional hints to detector
        multiple - if true, then the image is searched for multiple codes. If false, then at most one code will be found and returned
        Returns:
        PDF417DetectorResult encapsulating results of detecting a PDF417 code
        Throws:
        NotFoundException - if no PDF417 Code can be found

      • applyRotation

        private static BitMatrix applyRotation​(BitMatrix matrix,
                                       int rotation)
        Applies a rotation to the supplied BitMatrix.
        Parameters:
        matrix - bit matrix to apply rotation to
        rotation - the degrees of rotation to apply
        Returns:
        BitMatrix with applied rotation

      • detect

        private static java.util.List<ResultPoint[]> detect​(boolean multiple,
                                                    BitMatrix bitMatrix)
        Detects PDF417 codes in an image. Only checks 0 degree rotation
        Parameters:
        multiple - if true, then the image is searched for multiple codes. If false, then at most one code will be found and returned
        bitMatrix - bit matrix to detect barcodes in
        Returns:
        List of ResultPoint arrays containing the coordinates of found barcodes

      • findVertices

        private static ResultPoint[] findVertices​(BitMatrix matrix,
                                          int startRow,
                                          int startColumn)
        Locate the vertices and the codewords area of a black blob using the Start and Stop patterns as locators.
        Parameters:
        matrix - the scanned barcode image.
        Returns:
        an array containing the vertices: vertices[0] x, y top left barcode vertices[1] x, y bottom left barcode vertices[2] x, y top right barcode vertices[3] x, y bottom right barcode vertices[4] x, y top left codeword area vertices[5] x, y bottom left codeword area vertices[6] x, y top right codeword area vertices[7] x, y bottom right codeword area

      • copyToResult

        private static void copyToResult​(ResultPoint[] result,
                                 ResultPoint[] tmpResult,
                                 int[] destinationIndexes)

      • findRowsWithPattern

        private static ResultPoint[] findRowsWithPattern​(BitMatrix matrix,
                                                 int height,
                                                 int width,
                                                 int startRow,
                                                 int startColumn,
                                                 int minHeight,
                                                 int[] pattern)

      • findGuardPattern

        private static int[] findGuardPattern​(BitMatrix matrix,
                                      int column,
                                      int row,
                                      int width,
                                      int[] pattern,
                                      int[] counters)
        Parameters:
        matrix - row of black/white values to search
        column - x position to start search
        row - y position to start search
        width - the number of pixels to search on this row
        pattern - pattern of counts of number of black and white pixels that are being searched for as a pattern
        counters - array of counters, as long as pattern, to re-use
        Returns:
        start/end horizontal offset of guard pattern, as an array of two ints.

      • patternMatchVariance

        private static float patternMatchVariance​(int[] counters,
                                          int[] pattern)
        Determines how closely a set of observed counts of runs of black/white values matches a given target pattern. This is reported as the ratio of the total variance from the expected pattern proportions across all pattern elements, to the length of the pattern.
        Parameters:
        counters - observed counters
        pattern - expected pattern
        Returns:
        ratio of total variance between counters and pattern compared to total pattern size