Why do we use a blur function before edge detection?
Applying a low-pass blurring filter smooths edges and removes noise from an image. Blurring is often used as a first step before we perform Thresholding, Edge Detection, or before we find the Contours of an image. Larger sigma values may remove more noise, but they will also remove detail from an image.
How can I improve my edge detection?
2 Answers
- Read the input.
- Convert to gray.
- Threshold (as mask)
- Dilate the thresholded image.
- Compute the absolute difference.
- Invert its polarity as the edge image.
- Save the result.
What are the steps for edge detection?
The Canny edge detection algorithm is composed of 5 steps:
- Noise reduction;
- Gradient calculation;
- Non-maximum suppression;
- Double threshold;
- Edge Tracking by Hysteresis.
How do you add Gaussian Blur effect?
Go to Filter > Blur > Gaussian Blur, and the Gaussian Blur window will appear. You can drag the image in the Gaussian Blur window to look for the object you are going to blur. If you find it too small, tick the Preview box, and the result of the Gaussian Filter blur will be visible in the image.
How does edge detection work in a shader?
So, this shader is an implementation of the second algorithm described in William’s blog: Firstly, I add a property to use as a threshold to detect whether the values of the surrounding pixels differ significantly from the values of the sampled pixel. I also added a color property in case I wan’t to change the edge outline color.
Are there any effects that detect an edge?
Ever since I got into post-process effects, I was really curious to implement effects that do more complicated stuff than just change the color of the whole screen or play with depth. One such effect was an edge detection image effect, which seemed pretty simple, but the concept of detecting an edge eluded my simplistic way of thinking.
When does a shader return the original color?
If that length is larger than the threshold, the shader should return the edge color, otherwise it should return the original color. That’s how the combination of the lerp and step functions works in line 76.
Is the edge detection image effect aliased in Unity?
The shader is pretty straightforward, as it’s just an implementation of the algorithm in William’s blog. Do keep in mind, however, that the effect on it’s own can be quite aliased, and you would probably need to add some anti-aliasing from Unity’s post-processing stack.