OpenCV !_src.empty() in function 'cvtColor' error : <p>I am trying to do a basic colour conversion in python however I can't seem to get past the below error. I have re-installed python, opencv and tried on both python 3.4.3 (latest) and python 2.7 (which is on my Mac).</p>

<p>I installed opencv using python's package manager opencv-python. </p>

<p>Here is the code that fails:</p>

<pre><code>frame = cv2.imread('frames/frame%d.tiff' % count)
frame_HSV= cv2.cvtColor(frame,cv2.COLOR_RGB2HSV)
</code></pre>

<p>This is the error message:</p>

<pre><code>cv2.error: OpenCV(3.4.3) /Users/travis/build/skvark/opencv-python/opencv/modules/imgproc/src/color.cpp:181: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'
</code></pre>
