Relationship between brightness and the blurriness of an image

I wonder if anyone can explain what is the relationship between brightness (or Intensity) and the blurriness of an imag开发者_如何学Pythone..

I want to filter rank the blurred images using intensity as a parameter.

Examine the intensity levels in the frequency domain (FFT the image).

If there are high frequencies, image is not blurred. If all intensity is in low frequencies, image is blurred.

Alternatively, calculate Laplacian gradients of image, (for instance, current pixel * 4 - sum of 4 neighbors). If there are high gradients, image is not blurred, if there are none, image is blurred.

Edit: See Danny Varod's answer.

I don't think there is a relationship. (But believe your books/lecture notes over me.)

Imagine slowly increasing the intensity of the pixels (either straight up RGB or by another color scheme). The image will never get blurry, but it will continously "wash out" until it gets to the maximum intensity (say, 100% white).

Happy homeworking.

I probably have no idea what I'm talking about, but the amount of difference in brightness (contrast) can indicate sharpness or blurriness. Blurry images tend to have lower contrast than sharper images. Although, it isn't as simple as just knowing the highest and lowest brightness values, but also how quickly it changes between them. A large change over a small area indicates higher contrast than the same amount of change over a larger area.