i'm using OpenCV for Android.
I would like to know,how to make image correction(auto adjustments of brightness/contrast) for image(bitmap) in android via OpenCV or that can be done by native ColorMatrixFilter from Android!??
I tried to google,but didn't found good tutorials/examples.
So how can i achieve my goal? Any ideas?
Brightness and contrast is linear operator with parameter
In OpenCV you can do this with convertTo.
The question here is how to calculate
beta automatically ?
Looking at histogram, alpha operates as color range amplifier, beta operates as range shift.
Automatic brightness and contrast optimization calculates alpha and beta so that the output range is 0..255.
Histogram Wings Cut (clipping)
To maximize the result of it's useful to cut out some color with few pixels.
This is done cutting left right and wings of histogram where color frequency is less than a value (typically 1%). Calculating cumulative distribution from the histogram you can easly find where to cut.
may be sample chart helps to understand:
By the way
BrightnessAndContrastAuto could be named
normalizeHist because it works on BGR and gray images stretching the histogram to the full range without touching bins balance. If input image has range 0..255 BrightnessAndContrastAuto will do nothing.
Histogram equalization and CLAE works only on gray images and they change grays level balancing. look at the images below:
I am evaluating template matching algorithm to differentiate similar and dissimilar objects. What I found is confusing, I had an impression of template matching is a method which compares raw pixel intensity values. Hence when the pixel value varies I expected Template Matching to give a less match percentage.
I have a template and search image having same shape and size differing only in color(Images attached). When I did template matching surprisingly I am getting match percentage greater than 90%.
Template Image :
Search Image :
Can someone give me an insight why it is happening so? I have even tried this in HSV color space, Full BGR image, Full HSV image, Individual channels of B,G,R and Individual channels of H,S,V. In all the cases I am getting a good percentage.
Any help could be really appreciated.
三、likely position of Feature Matching.
I am using Brute Force Matcher with L2 norm. Referring this link https://docs.opencv.org/2.4/doc/tutor...
After the process, I get below image as output
What is the likely position of the object suggested by the feature matching?
I don't understand how to choose the likely position using this image :(
to retrieve the position of your matched object, you need some further steps :
The cv::Mat is a CDOcument variable member:
and I draw rectangles over image, with an method (called at some time intervals, according FPS rate):
Here is the code of this method:
but the result of this method is something like that:
My question is: how can I draw only the last blobs result over my image ?
I have tried to clean up m_Mat, and to enable to draw only blobs.size() - 1 blob over image, none of this worked ...
五、How to find the thickness of the red color sealent in the image ????
I want to find the thickness of the red colored sealent in the image.
First I'm extracting the sealent portion by using findcontours by having minimum and maximum conotur area.And then check the Area,length and thickness of the sealent,i can find the area as well as length but i m not able to find the thickness of the sealent portion.
Please help me guys........below is the example image.