Fixing the "Assertion Failed" Error in `take_screenshot_with_ocr`
You might encounter an error when using the take_screenshot_with_ocr tool in the computer-control-mcp project. Specifically, the error message will look something like this:
OpenCV(4.12.0) D:\a\opencv-python\opencv-python\opencv\modules\imgproc\src\resize.cpp:4211: error: (-215:Assertion failed) inv_scale_x > 0 in function 'cv::resize'
This error arises during the image resizing process within the take_screenshot_with_ocr function. It indicates that OpenCV, the image processing library, is encountering an invalid scaling factor when attempting to resize the screenshot.
Understanding the Root Cause
The core issue lies in the parameters passed to the cv2.resize() function. The error message "inv_scale_x > 0" suggests that the calculated inverse scaling factor for the x-axis (width) is not a positive value. This typically happens when the target dimensions for the resized image are invalid, potentially zero or negative.
In the context of the take_screenshot_with_ocr function, this could be due to incorrect calculations related to the desired output size or issues with the initial image dimensions before resizing. The specific cause could vary depending on the input image and how the target dimensions `dim` are being determined.
Solution: Upgrading to Version 0.3.10 or Later
The quickest and recommended solution is to upgrade your computer-control-mcp package to version 0.3.10 or later. This version includes a patch that addresses the reported issue. You can upgrade using pip:
pip install computer_control_mcp --upgrade
After running this command, verify that the package has been updated to the correct version:
pip show computer_control_mcp
This will display information about the installed package, including its version. Ensure that the version is 0.3.10 or greater.
Alternative Solutions (If Upgrading Isn't Immediately Possible)
If you cannot upgrade immediately, you can try debugging the issue by examining the dimensions used in the cv2.resize() function. Locate the following line in your local copy of the computer_control_mcp\core.py file (usually found within your Python environment's site-packages directory):
resized_img = cv2.resize(img, dim, interpolation=cv2.INTER_AREA)
Add print statements to inspect the values of img.shape and dim just before this line:
print(f"Original image shape: {img.shape}")
print(f"Target dimensions: {dim}")
resized_img = cv2.resize(img, dim, interpolation=cv2.INTER_AREA)
Run your code again and analyze the output. Ensure that both the width and height components of dim are positive integers. If either dimension is zero or negative, you'll need to adjust the logic that calculates these dimensions. If the original image has zero width or height, that will also cause this error.
Practical Considerations
- Check Image Input: Ensure that the image being passed to
take_screenshot_with_ocris valid and has non-zero dimensions. - Dimension Calculations: Review the code responsible for calculating the target dimensions (
dim). Verify that the calculations are correct and produce positive values. - OpenCV Version: While the error message mentions OpenCV 4.12.0, upgrading to the latest version of OpenCV might also resolve underlying compatibility issues. You can upgrade OpenCV using:
pip install opencv-python --upgrade
By upgrading to version 0.3.10 or later, or carefully inspecting the image dimensions, you should be able to resolve this "Assertion Failed" error and successfully use the take_screenshot_with_ocr tool.