I have a dataset consisting of different characters. I need an approch to combine two classifiers KNN and SVM to classify these characters instead of using one in isolation.
I do have an answer for the the question but it would finally conclude what Antonios Georgantzoglou is saying. So my support to that answer gives more support to you to implement.
Why not try locally (linear and nonlinear) SVM (LL SVM) classifiers. In short, it designs SVM for some local neighborhood of k-data. Alternatively try ALH approach, but LL SVM is more accurate, although slower. Download my papers on ALH and LL SVM from research gate site here. Good luck.
If your dataset is known, fixed and relatively reduced in size, k-NN would fit much better. Although SVN can provide better accuracy in some classification problems, I would not recommend it due to several drawbacks: lots of parameters to be tuned, increased complexity, difficulties to be extended for multi-class classification.
If your dataset is not fully labeled, then you should do it somehow especially if you are dealing with real-time classification processes. You can use some hybrid k-means clustering approaches to label the data and find the patterns. Then you can use some types of neural networks to sort out with approximation and generalization issues.