基于多特征SAD-Census变换的立体匹配算法

吴福培; 黄耿楠; 刘宇豪; 叶玮琳; 李昇平

doi:10.37188/CO.2023-0082

基于多特征SAD-Census变换的立体匹配算法

doi: 10.37188/CO.2023-0082

汕头大学工学院机械工程系, 广东汕头 515063

基金项目: 国家自然科学基金（No. 61573233）；广东省自然科学基金（No. 2021A1515010661）；广东省普通高校重点领域专项（No. 2020ZDZX2005）

详细信息

作者简介:
吴福培（1980—），男，广西玉林人，博士，教授，2009年于华南理工大学机械工程专业获得博士学位，现就职于汕头大学机械工程系，主要研究方向：自动光学检测和3D测量。E-mail：fpwu@stu.edu.cn

黄耿楠（1997—），男，广东揭阳人，硕士， 2023年于汕头大学机械工程专业获得硕士学位，现就职于比亚迪有限公司，担任高级工程师。研究方向：双目视觉与三维测量。E-mail：907877156@qq.com

刘宇豪（1999—），男，重庆人，硕士研究生，主要研究方向：双目视觉与三维测量。E-mail：21yhliu@stu.edu.cn

叶玮琳（1984—），女，广东潮州人，副教授，博士，主要研究方向：光电传感技术。E-mail：wlye@stu.edu.cn

李昇平（1966—），男，湖南永州人，教授，博士，主要研究方向：自适应控制、机器视觉。E-mail：spli@stu.edu.cn

中图分类号: TP391.4
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出版历程
- 收稿日期: 2023-05-08
- 修回日期: 2023-06-02
- 网络出版日期: 2023-09-15

Stereo matching algorithm based on multi-feature SAD-Census transformation

Department of Mechanical Engineering, College of Engineering, Shantou University, Shantou 515063, China

Funds: Supported by National Natural Science Foundation of China (No. 6l573233); Natural Science Foundation of Guangdong Province (No. 2021A1515010661); Special Projects in Key Areas of General Universities in Guangdong Province (No. 2020ZDZX2005)

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Corresponding author: 907877156@qq.com

摘要

摘要:
视差不连续区域和重复纹理区域的误匹配率高一直是影响双目立体匹配测量精度的主要问题，为此，本文提出一种基于多特征融合的立体匹配算法。首先，在代价计算阶段，通过高斯加权法赋予邻域像素点的权值，从而优化绝对差之和（Sum of Absolute Differences，SAD）算法的计算精度。接着，基于Census变换改进二进制链码方式，将邻域内像素的平均灰度值与梯度图像的灰度均值相融合，进而建立左右图像对应点的判断依据并优化其编码长度。然后，构建基于十字交叉法与改进的引导滤波器相融合的聚合方法，从而实现视差值再分配，以降低误匹配率。最后，通过赢家通吃（Winner Take All，WTA）算法获取初始视差，并采用左右一致性检测方法及亚像素法提高匹配精度，从而获取最终的视差结果。实验结果表明，在Middlebury数据集的测试中，所提SAD-Census算法的平均非遮挡区域和全部区域的误匹配率为分别为2.67%和5.69%，测量200~900 mm距离的平均误差小于2%；而实际三维测量的最大误差为1.5%。实验结果检验了所提算法的有效性和可靠性。
- 机器视觉 /
- 立体匹配 /
- SAD-Census变换 /
- 十字交叉法 /
- 引导滤波
Abstract:
The high mismatching rate of the parallax discontinuity region and the repeated texture region has been a major issue affecting the measurement accuracy of binocular stereo matching. For these reasons, we propose a stereo matching algorithm based on multi-feature fusion. Firstly, the weight of neighboring pixels is given using Gaussian weighting method, which optimizes the calculation accuracy of the Sum of Absolute Differences (SAD) algorithm. Based on the Census transformation, the binary chain code technique has been enhanced to fuse the average gray value of neighborhood pixels with the average gray value of gradient image, and then the judgment basis of the left and right image corresponding points is established, and the coding length is optimized. Secondly, an aggregation technique has been developed that combines the cross method and the improved guide filter to redistribute disparity values with the aim of minimizing false matching rate. Finally, the initial disparity is obtained by the Winner Take All (WTA) algorithm, and the final disparity results are obtained by the left-right consistency detection method, sub-pixel method, and then a stereo matching algorithm based on the multi-feature SAD Census transform is established. The experimental results show that in the testing of the Middlebury dataset, the average mismatch rates of the proposed algorithm for non-occluded regions and all regions are 2.67% and 5.69%, the average error of the 200−900 mm distance is less than 2%, and the maximum error of the actual 3D data measurement is 1.5%. Experimental results verify the effectiveness of the proposed algorithm.
- machine vision /
- stereo matching /
- SAD-Census transform /
- cross method /
- guided filtering

HTML全文

图 1 改进Census变换示意图

Figure 1. Schematic diagram of improved Census transform

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图 2 自适应十字交叉域

Figure 2. Adaptive crossing domain

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图 3 优化聚合路径示意图

Figure 3. Schematic diagram of optimized aggregation path

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图 4 3种代价计算方法的视差图。（a）传统SAD-Census算法；（b）传统SAD+改进Census算法；（c）本文算法

Figure 4. Parallax maps of three cost calculation methods. (a) Traditional SAD-Census algorithms; (b) traditional SAD + improved Census algorithm; (a) the proposed algorithm

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图 5 4种算法的实验结果图

Figure 5. Experimental results of 4 kinds of algorithms

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图 6 不同算法的误匹配率

Figure 6. Mismatch rate of different algorithms

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图 7 不同亮度下几种算法的实验结果

Figure 7. Experimental results of 4 kinds of algorithms at different brightness levels

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图 8 噪声干扰下各算法的实验结果

Figure 8. Experimental results of different algorithms under noise interference

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图 9 测距实验对比结果

Figure 9. Comparison results of distance measuring experiments

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图 10 样本视差结果图的边缘提取

Figure 10. Edge extraction of sample parallax result maps

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图 11 量块视差图

Figure 11. Gauge block parallax map

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表 1 实验参数设置

Table 1. Experimental parameter setting

Parameter	Value	Parameter	Value
б	2	λ	0.003
τ₁	16	ε	0.001
τ₂	4	ω	9×7
L₁	30	β₁	0.6
L₂	15	β₂	0.4
δ₀	1

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表 2 不同算法在非遮挡区域和全部区域的误匹配率

Table 2. Mismatch rate of different algorithms in the non-occluded region and all regions (%)

Algorithm	Tsukuba			Venus			Teddy			Cones			Avg
Algorithm	Non	all	Disc	Non	all	Disc	Non	all	Disc	Non	all	Disc	Non	all	Disc
GC-occ	1.19	2.01	6.24	1.64	2.19	6.75	11.20	17.40	19.80	5.36	12.40	13.00	4.84	8.50	11.45
SemiGlob	3.26	3.96	12.80	1.00	1.57	11.30	6.02	12.20	16.30	3.06	9.75	8.90	3.34	6.87	12.32
RTCensus	5.08	6.25	19.20	1.58	2.42	14.20	7.96	13.8	20.30	4.10	9.54	12.20	4.68	8.01	16.48
HCA	1.31	2.47	0.94	0.11	0.23	0.24	4.23	9.45	3.67	5.64	11.59	4.30	2.83	5.94	2.29
Cross-ScaleGF	2.38	2.85	8.40	1.13	1.98	9.26	7.05	14.9	16.80	3.32	11.00	7.99	3.47	7.68	10.61
GradAdaptWgt	2.26	2.63	8.99	0.99	1.39	4.92	8.00	13.10	18.60	2.61	7.67	7.43	3.46	6.19	9.99
Proposed algorithm	1.25	2.73	0.90	0.15	0.31	0.31	4.62	8.73	2.98	4.69	10.98	4.11	2.67	5.69	2.08

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表 3 三维测距实验结果

Table 3. Experimental results of three-dimensional distance measurement

序号	实际距离/mm	测量距离/mm	距离误差/mm	距离误差率/%
1	200	198.42	−1.58	0.79
2	300	302.55	2.55	0.85
3	400	403.76	3.76	0.94
4	500	495.05	−4.95	0.99
5	600	606.06	6.06	1.01
6	700	707.56	7.56	1.08
7	800	809.52	9.52	1.19
8	900	912.24	12.24	1.36

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表 4 测量样本实验结果

Table 4. Sample experimental results

样本序号	实际长度/mm	测量长度/mm	误差/mm	误差率/%
1	20	19.9575	−0.0425	−0.21
1	35	34.6144	−0.3856	−1.1
2	35	35.1649	0.1649	−0.47
2	50	49.9672	−0.0328	−0.06
3	5	4.9439	−0.0561	−1.12
3	15	14.7565	−0.2435	−1.62
4	20	20.3541	0.3541	0.71
4	30	29.5784	−0.4216	−1.41

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表 5 厚度测量结果

Table 5. Thickness measurement results

序号	实际厚度/mm	测量厚度/mm	测量误差/mm	绝对误差率/%
1	1.00	1.0105	0.0105	1.05
2	1.10	1.1235	0.0235	2.13
3	1.20	1.2335	0.0335	2.79
4	1.50	1.5563	0.0563	3.75
5	2.00	1.9346	−0.0654	3.27

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