clc;
clear;
%% 加载2张立体图像
left = imread('tsuL.png');
right = imread('tsuR.png');
sizeI = size(left);
% 显示复合图像
zero = zeros(sizeI(1), sizeI(2));
channelRed = left(:,:,1);
channelBlue = right(:,:,3);
composite = cat(3, channelRed, zero, channelBlue);
figure;
subplot(1,2,1);
imshow(left);
axis image;
title('Left Image');
subplot(1,2,2);
imshow(right);
axis image;
title('Right Image');
figure;
imshow(composite);
axis image;
title('Composite Image');
%% 基本的块匹配
% 通过估计子像素的块匹配计算视差
disp('运行基本的块匹配~');
% 启动定时器
tic();
% 平均3个颜色通道值将RGB图像转换为灰度图像
leftI = mean(left, 3);
rightI = mean(right, 3);
% SHD
bitsUint8 = 8;
leftI = im2uint8(leftI./255.0);
rightI = im2uint8(rightI./255.0);
% DbasicSubpixel将保存块匹配的结果,元素值为单精度32位浮点数
DbasicSubpixel = zeros(size(leftI), 'single');
% 获得图像大小
[imgHeight, imgWidth] = size(leftI);
% 视差范围定义离第1幅图像中的块位置多少像素远来搜索其它图像中的匹配块。对于大小为450x375的图像,视差范围为50是合适的
disparityRange = 50;
% 定义块匹配的块大小
halfBlockSize = 5;
blockSize = 2 * halfBlockSize + 1;
% 对于图像中的每行(m)像素
for (m = 1 : imgHeight)
% 为模板和块设置最小/最大块边界
% 比如:第1行,minr = 1 且 maxr = 4
minr = max(1, m - halfBlockSize);
maxr = min(imgHeight, m + halfBlockSize);
% 对于图像中的每列(n)像素
for (n = 1 : imgWidth)
% 为模板设置最小/最大边界
% 比如:第1列,minc = 1 且 maxc = 4
minc = max(1, n - halfBlockSize);
maxc = min(imgWidth, n + halfBlockSize);
% 将模板位置定义为搜索边界,限制搜索使其不会超出图像边界
% 'mind'为能够搜索至左边的最大像素数;'maxd'为能够搜索至右边的最大像素数
% 这里仅需要向右搜索,所以mind为0
% 对于要求双向搜索的图像,设置mind为max(-disparityRange, 1 - minc)
mind = 0;
maxd = min(disparityRange, imgWidth - maxc);
% 选择右边的图像块用作模板
template = rightI(minr:maxr, minc:maxc);
% 获得本次搜索的图像块数
numBlocks = maxd - mind + 1;
% 创建向量来保存块偏差
blockDiffs = zeros(numBlocks, 1);
% 计算模板和每块的偏差
for (i = mind : maxd)
%选择左边图像距离为'i'处的块
block = leftI(minr:maxr, (minc + i):(maxc + i));
% 计算块的基于1的索引放进'blockDiffs'向量
blockIndex = i - mind + 1;
%{
% NCC(Normalized Cross Correlation)
ncc = 0;
nccNumerator = 0;
nccDenominator = 0;
nccDenominatorRightWindow = 0;
nccDenominatorLeftWindow = 0;
%}
% 计算模板和块间差的绝对值的和(SAD)作为结果
for (j = minr : maxr)
for (k = minc : maxc)
%{
% SAD(Sum of Absolute Differences)
blockDiff = abs(rightI(j, k) - leftI(j, k + i));
% SSD(Sum of Squared Differences)
% blockDiff = (rightI(j, k) - leftI(j, k + i)) * (rightI(j, k) - leftI(j, k + i));
blockDiffs(blockIndex, 1) = blockDiffs(blockIndex, 1) + blockDiff;
%}
%{
% NCC
nccNumerator = nccNumerator + (rightI(j, k) * leftI(j, k + i));
nccDenominatorLeftWindow = nccDenominatorLeftWindow + (leftI(j, k + i) * leftI(j, k + i));
nccDenominatorRightWindow = nccDenominatorRightWindow + (rightI(j, k) * rightI(j, k));
%}
end
end
%{
% SAD
blockDiffs(blockIndex, 1) = sum(sum(abs(template - block)));
%}
%{
% NCC
nccDenominator = sqrt(nccDenominatorRightWindow * nccDenominatorLeftWindow);
ncc = nccNumerator / nccDenominator;
blockDiffs(blockIndex, 1) = ncc;
%}
% SHD(Sum of Hamming Distances)
blockXOR = bitxor(template, block);
distance = uint8(zeros(maxr - minr + 1, maxc - minc + 1));
for (k = 1 : bitsUint8)
distance = distance + bitget(blockXOR, k);
end
blockDiffs(blockIndex, 1) = sum(sum(distance));
end
% SAD值排序找到最近匹配(最小偏差),这里仅需要索引列表
% SAD/SSD/SHD
[temp, sortedIndeces] = sort(blockDiffs, 'ascend');
%{
% NCC
[temp, sortedIndeces] = sort(blockDiffs, 'descend');
%}
% 获得最近匹配块的基于1的索引
bestMatchIndex = sortedIndeces(1, 1);
% 将该块基于1的索引恢复为偏移量
% 这是基本的块匹配产生的最后的视差结果
d = bestMatchIndex + mind - 1;
%{
% 通过插入计算视差的子像素估计
% 子像素估计要求用左右边的块, 所以如果最佳匹配块在搜索窗的边缘则忽略估计
if ((bestMatchIndex == 1) || (bestMatchIndex == numBlocks))
% 忽略子像素估计并保存初始视差值
DbasicSubpixel(m, n) = d;
else
% 取最近匹配块(C2)的SAD值和最近的邻居(C1和C3)
C1 = blockDiffs(bestMatchIndex - 1);
C2 = blockDiffs(bestMatchIndex);
C3 = blockDiffs(bestMatchIndex + 1);
% 调整视差:估计最佳匹配位置的子像素位置
DbasicSubpixel(m, n) = d - (0.5 * (C3 - C1) / (C1 - (2 * C2) + C3));
end
%}
DbasicSubpixel(m, n) = d;
end
% 每10行更新过程
if (mod(m, 10) == 0)
fprintf('图像行:%d / %d (%.0f%%)\n', m, imgHeight, (m / imgHeight) * 100);
end
end
% 显示计算时间
elapsed = toc();
fprintf('计算视差图花费 %.2f min.\n', elapsed / 60.0);
%% 显示视差图
fprintf('显示视差图~\n');
% 切换到图像4
figure
% 第2个参数为空矩阵,从而告诉imshow用数据的最小/最大值,并且映射数据范围来显示颜色
imshow(DbasicSubpixel, []);
% 去掉颜色图会显示灰度视差图
colormap('jet');
colorbar;
% 指定视差图的最小/最大值
%caxis([0 disparityRange]);
%设置显示的标题
title(strcat('Basic block matching, Sub-px acc., Search left, Block size = ', num2str(blockSize)));