感兴趣的区域与透明背景的小图像

Question

我想从给定掩码的图像中提取感兴趣区域（ROI），并将其保存在调整为ROI大小的新文件中，并保留透明背景。

例如给出这个图像：

我想得到这个：

此处的解决方案NumPy/OpenCV 2: how do I crop non-rectangular region?以完整大小提供输出图像。如何让它输出ROI的矩形尺寸？

我可以按位<ion-view view-title="Chats"> <ion-content> <ion-list can-swipe="true"> <ion-item gesture-type="swipeRight" on-swipe-right="swipeRight()" class="item-remove-animate item-avatar item-icon-right" ng-repeat="chat in chats" type="item-text-wrap" href="#/tab/chats/{{chat.id}}"> <img ng-src="{{chat.face}}"> <h2>{{chat.name}}</h2> <p>{{chat.lastText}}</p> <i class="icon ion-chevron-right icon-accessory"></i> <ion-option-button class="button-assertive" ng-click="share(item)" side="left"> Share </ion-option-button> <ion-option-button class="button-assertive" ng-click="remove(chat)" side="right"> Delete </ion-option-button> </ion-item> </ion-list> </ion-content> </ion-view> 图像和蒙版，但我真的很困惑一种调整图像大小并将其保存为透明png的好方法。

Answer 1

这个图像（1.jpg）与脚本
在同一个文件夹中

以下蒙面图片：

我写了一个非常讨厌的解决方案。

import numpy as np                                                                                                                                                                                                          
import sys
import cv2        

image = cv2.imread('1.jpg')

# mask (of course replace corners with yours)
mask = np.zeros(image.shape, dtype=np.uint8)
roi_corners = np.array([[(10,10), (200,200), (10,200)]], dtype=np.int32)
white = (255, 255, 255)
cv2.fillPoly(mask, roi_corners, white)

# apply the mask
masked_image = cv2.bitwise_and(image, mask)


#shrink the top
iii = 0
#the matrix sum of back is 0
while  not np.sum(masked_image[iii,:,:]):
        resized_top = masked_image[iii+1:,:,:]
            iii = iii + 1


#shrink the bottom
size_img = resized_top.shape
iii = size_img[0]
while not np.sum(resized_top[iii-2:iii-1,:,:]):
        resized_bottom = resized_top[0:iii-1,:,:]
            iii = iii - 1

#shrink the left
iii = 0
while  not np.sum(resized_bottom[:,iii,:]):
        resized_left = resized_bottom[:,iii+1:,:]
            iii = iii + 1

#shrink the right
size_img = resized_left.shape
iii = size_img[1]
print iii
while  not np.sum(resized_left[:,iii-2:iii-1,:]):
        resized_right = resized_left[:,0:iii-1:,:]
            iii = iii - 1


#display your handywork
cv2.imshow('masked image', resized_right)
cv2.waitKey()
cv2.destroyAllWindows()

结果：

Answer 2

可以通过

来实现裁剪图像

cropped_img = masked_image[y1:y2, x1:x2]

首先必须计算投资回报率的矩形边界框。