Is there a simple algorithm for calculating an acutance value (or sharpness) for a grayscale image?
As I understand it, the Accutance is the mean value of the Gradient Filter.
Example in Mathematica:
Relationship between brightness and the blurriness of an image
The question's title is confusing, but the answer answers this.
Related
I am using Kinect2 with Matlab; however, the depth images shown in the video stream are much brighter than when I saved it in Matlab?
do you know the solution for this problem
Firstly, you should provide the code that you are using at the moment so we can see where you are going wrong.. this is a generic advice for posting on any forum; to provide with all your information, so others can help.
If you use the histogram to check your depth values, you will see that the image is a uint8 image with values from 0 to 255. And since the depth distances are scaled to grayscale value, the values are scaled to new values and using imshow, will not provide enough contrast.
An easy workaround for displaying images is to use any type of
histogram equalization such as
figure(1);
C= adapthisteq(A, 'clipLimit',0.02,'Distribution','rayleigh');
imshow(C);
The image will be contrast adjusted for display.
I used mat2gray and it solved the problem.
I am now working on the interpolation of gray value for an image. I wanna use the matlab function griddedInterpolant. For the interpolation method it has 'cubic' and 'spline'. Both of them are C2 continues. I have found the algorithm about 'cubic' (actually 'bicubic' since my data are 2D) as listed in WiKipedia:
https://en.wikipedia.org/wiki/Bicubic_interpolation.
I wanna ask if some one know the algorithm behind 'spline' (actually 'bicubic spline' for 2D). Because I don't quite understand the difference between them.
And for my calculation I need the gradient of the gray value too. Since in function griddedInterpolant it is not possible to get the coefficients of the interpolation, there's no way to calculate the gradients directly.
Can someone help me with that?
If I resize an image in MATLAB, what effect will that have on the original image. Say for instance I have an image of size 437x167 and I want to resize it to 256x256. Will there be any details that will go missing from such operation?
Thanks.
if i understand you correctly you mean: "what are the results on an image after using matlab's built in function imresize?" by looking at the documentation of imresize you can see that you can choose what algorithm you want to use through the parameters of imresize. the best answer can be found by googeling the respective algorithms and reading what is the data loss caused by each of these algorithms
Folks,
I have read a number of articles on Discrete Wavelet Transform (DWT) and looked at some sample code as well. However, I am not clear on what exactly does DWT achieve.
Here is what I understand. For a two dimensional image in YUV format, I can pass in the Y plane (brightness) to DWT function as a parameter. The function returns me a matrix of the original width and height containing coefficient values.
What are these coefficient values telling me? Is it how fast or slow the brightness of a pixel has changed compared to its neighbors?
Further, the returned matrix is rearranged in four quarters. As the coefficients have been rearranged, I no longer know which coefficient belongs to which pixel. This is confusing. If I cannot associate the coefficient to its corresponding pixel location, how can I really use the coefficients?
A little bit of background. I am looking at hiding some information in an image as an invisible watermark. From what I understand, DWT can help me identify the best region to hide the information. However, I have not been able to put the whole picture together.
Ok. I figured out how DWT works. I was under the assumption that the coefficients generated have a relationship with the original image. However, the transform converts the input luma into a completely different set. It is possible to run the reverse transform on the new values to once again obtain the original values.
Regards,
Peter
Recently I saw demonstration of image distortion algorithm that preserves some objects in image. For example changing weight/height ratio but preserving people faces in image to look realistically. The problem is i can't find the reference to that demonstration neither I know the name of such transformations.
Can anybody point me to a references to such algorithms?
Perhaps you are referring to liquid rescale?
Seam carving is the current favourite. Liquid Rescale is an implementation of it.