add contour image, check folder, fix some error

.ipynb_checkpoints/openCV_scanner-checkpoint.ipynb

Untitled.ipynb

contour/document.jpg

contour/example.jpg

contour/example2.jpg

contour/example2.png

contour/example3.jpg.png

contour/receipt.jpg

contour/receipt2.jpg

contour/tilted receipt.jpg

contours/document.jpg

contours/receipt2.jpg

contours/tilted receipt.jpg

images/example.jpg

images/example2.jpg

images/example2.png

images/example3.jpg.png

images/receipt.jpg

modified/document.jpg

modified/example.jpg