将像素从图像的裁剪部分转换为原始图像 OpenCV答案

【问题标题】：Translate pixels from cropped section of image to original image OpenCV将像素从图像的裁剪部分转换为原始图像 OpenCV
【发布时间】：2018-01-08 19:24:52
【问题描述】：

我在 Python 中使用 OpenCV。我使用以下代码选择主图像的一部分并将其复制到子图像中：

boundingBoxRotatedRect = cv2.minAreaRect(boxPoints)
if boundingBoxRotatedRect[2] < -45:
    boundingBoxRotatedRect = (boundingBoxRotatedRect[0], (boundingBoxRotatedRect[1][1],boundingBoxRotatedRect[1][0]), boundingBoxRotatedRect[2] + 90)
M = cv2.getRotationMatrix2D(boundingBoxRotatedRect[0], boundingBoxRotatedRect[2], 1.0)  
size = np.int0(boundingBoxRotatedRect[1])
size = (size[0],size[1])
dst = cv2.warpAffine(mainImage, M, (mainImage.shape[1], mainImage.shape[0]))
subImage = cv2.getRectSubPix(dst, size, boundingBoxRotatedRect[0])

其中 boxPoints 是一个由 4 个点组成的数组，构成从主图像中要裁剪的区域周围的边界框，boundingBoxRotatedRect 是表示为旋转矩形对象的同一个框，M 是旋转矩阵，size 是宽度/边界框的高度，mainImage 是被裁剪的主图像，而 subImage 最终是从主图像裁剪的最终图像。下面链接的图片进一步解释了正在发生的事情。

Explanation Image

我的问题是：如果我使用 OpenCV 绘图功能来编辑 subImage，我怎样才能将这些相同的绘图放回 mainImage 的相应像素上？例如（如果使用我提供的解释图像中的图像形状）我在 subImage 上绘制了一个直立的笑脸，我如何将其转换为 mainImage 上正确位置的正确定向的对角笑脸？

【问题讨论】：

标签： python image opencv image-processing image-manipulation

【解决方案1】：

找到了解决办法。同名！

将上面的代码替换为：

#If bottomLeft = true, boxPoints[0] corresponds to btm-lft corner of subImage. 
#If bottomLeft = false, boxPoints[0] corresponds to btm-right corner of subImage. 
bottomLeft = True 

boundingBoxRotatedRect = cv2.minAreaRect(boxPoints)
if boundingBoxRotatedRect[2] < -45:
    boundingBoxRotatedRect = (boundingBoxRotatedRect[0], (boundingBoxRotatedRect[1][1],boundingBoxRotatedRect[1][0]), boundingBoxRotatedRect[2] + 90)
    bottomLeft = False
M = cv2.getRotationMatrix2D(boundingBoxRotatedRect[0], boundingBoxRotatedRect[2], 1.0)  
size = np.int0(boundingBoxRotatedRect[1])
size = (size[0],size[1])
dst = cv2.warpAffine(mainImage, M, (mainImage.shape[1], mainImage.shape[0]))
subImage = cv2.getRectSubPix(dst, size, boundingBoxRotatedRect[0])

#Get homography matrix
if bottomLeft:
    pts_src = np.array([[0, size[0] - 1], [0, 0], [size[1] - 1, 0],[size[1] - 1, size[0] - 1]])
else:
    pts_src = np.array([[size[1] - 1, size[0] - 1], [0, size[0] - 1], [0, 0], [size[1] - 1, 0]])
pts_dst = boxPoints
h, status = cv2.findHomography(pts_src, pts_dst)


## BELOW, REPLACE "[x, y], [X2, Y2], ...]" WITH LIST OF POINTS FROM SUBIMAGE TO BE TRANSLATED TO MAINIMAGE
a = np.array([[x, y], [X2, Y2], ...] dtype='float32')
a = np.array([a])
pointsOut = cv2.perspectiveTransform(a, h)
pointsOut = pointsOut[0]

#Then use the points in pointsOut to draw whatever you want!

【讨论】：