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[WeChat QR] Fixing issue that Hybrid Binarizer not working due to integral calculation. #3199

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Merged
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Apr 1, 2022
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[WeChat QR] Fixing issue that Hybrid Binarizer not working due to integral calculation. #3199

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29 changes: 12 additions & 17 deletions modules/wechat_qrcode/src/zxing/common/binarizer/hybrid_binarizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,9 @@ Ref<Binarizer> HybridBinarizer::createBinarizer(Ref<LuminanceSource> source) {
}

int HybridBinarizer::initBlockIntegral() {
blockIntegral_ = new Array<int>(width * height);
blockIntegralWidth = subWidth_ + 1;
blockIntegralHeight = subHeight_ + 1;
blockIntegral_ = new Array<int>(blockIntegralWidth * blockIntegralHeight);

int* integral = blockIntegral_->data();

Expand All @@ -64,34 +66,27 @@ int HybridBinarizer::initBlockIntegral() {
// first row only
int rs = 0;

for (int j = 0; j < width; j++) {
for (int j = 0; j < blockIntegralWidth; j++) {
integral[j] = 0;
}

for (int i = 0; i < height; i++) {
integral[i * width] = 0;
}

for (int j = 0; j < subWidth_; j++) {
rs += blocks_[j].threshold;
integral[width + j + 1] = rs;
for (int i = 0; i < blockIntegralHeight; i++) {
integral[i * blockIntegralWidth] = 0;
}

// remaining cells are sum above and to the left
int offset = width;
int offsetBlock = 0;
int offsetIntegral = 0;

for (int i = 1; i < subHeight_; ++i) {
for (int i = 0; i < subHeight_; ++i) {
// therow = grayByte_->getByteRow(i);
offsetBlock = i * subWidth_;

offsetIntegral = (i + 1) * blockIntegralWidth;
rs = 0;

offset += width;

for (int j = 0; j < subWidth_; ++j) {
rs += blocks_[offsetBlock + j].threshold;
integral[offset + j + 1] = rs + integral[offset - width + j + 1];
integral[offsetIntegral + j + 1] = rs + integral[offsetIntegral - blockIntegralWidth + j + 1];
}
}

Expand Down Expand Up @@ -201,8 +196,8 @@ void HybridBinarizer::calculateThresholdForBlock(Ref<ByteMatrix>& _luminances, i
int sum = 0;
// int sum2 = 0;

int offset1 = (top - THRES_BLOCKSIZE) * (subWidth + 1) + left - THRES_BLOCKSIZE;
int offset2 = (top + THRES_BLOCKSIZE + 1) * (subWidth + 1) + left - THRES_BLOCKSIZE;
int offset1 = (top - THRES_BLOCKSIZE) * blockIntegralWidth + left - THRES_BLOCKSIZE;
int offset2 = (top + THRES_BLOCKSIZE + 1) * blockIntegralWidth + left - THRES_BLOCKSIZE;

int blocksize = THRES_BLOCKSIZE * 2 + 1;

Expand Down
2 changes: 2 additions & 0 deletions modules/wechat_qrcode/src/zxing/common/binarizer/hybrid_binarizer.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@ class HybridBinarizer : public GlobalHistogramBinarizer {

int subWidth_;
int subHeight_;
int blockIntegralWidth;
int blockIntegralHeight;
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@alalek alalek Mar 30, 2022 •
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I don't see code changes related to reading of blockIntegral_ with new layout. I see changes in "generator" only.

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@ninh-huynh ninh-huynh Mar 31, 2022

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It took me a while to understand the logic in here due to unclear meaning of left, top, offset1, offset2

opencv_contrib/modules/wechat_qrcode/src/zxing/common/binarizer/hybrid_binarizer.cpp

Lines 198 to 210 in 7a35d3d

int left = cap(x, THRES_BLOCKSIZE, subWidth - THRES_BLOCKSIZE - 1);
int top = cap(y, THRES_BLOCKSIZE, subHeight - THRES_BLOCKSIZE - 1);
int sum = 0;
// int sum2 = 0;
int offset1 = (top - THRES_BLOCKSIZE) * (subWidth + 1) + left - THRES_BLOCKSIZE;
int offset2 = (top + THRES_BLOCKSIZE + 1) * (subWidth + 1) + left - THRES_BLOCKSIZE;
int blocksize = THRES_BLOCKSIZE * 2 + 1;
sum = blockIntegral[offset1] - blockIntegral[offset1 + blocksize] -
blockIntegral[offset2] + blockIntegral[offset2 + blocksize];

As my understanding, the left, top correspond to centerX, centerY of 5 x 5 block square. And offset1, offset2 are A, C in

A - - B
|        |
C - - D

The blockIntegral is already used with new layout so we don't need to modify anything in there.

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@ninh-huynh ninh-huynh Mar 31, 2022

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For more clear, we could change subWidth + 1 to blockIntegralWidth in here

opencv_contrib/modules/wechat_qrcode/src/zxing/common/binarizer/hybrid_binarizer.cpp

Lines 204 to 205 in 7a35d3d

int offset1 = (top - THRES_BLOCKSIZE) * (subWidth + 1) + left - THRES_BLOCKSIZE;
int offset2 = (top + THRES_BLOCKSIZE + 1) * (subWidth + 1) + left - THRES_BLOCKSIZE;


public:
explicit HybridBinarizer(Ref<LuminanceSource> source);
Expand Down