Image procs techniques for apple grading based on color

My topic is to analyze the quality of fruit(apple) based on image processing. In this firstly take the image in RGB model but for extarcting the colour component from apple, convert RGB image into HSI model and take the hue component from HSI image. Steps involved in MATLAB simulation: 1. RGB image 2. Select Region of interest (ROI) by segment the colour component like only detect the colour surface of apple and ignore the white portion [login to view URL] to HSI [login to view URL] HUE component 5. Auto analysis of colour based on hue histogram [login to view URL] grade based on analysis 7. dispaly the result But there is some problem in ROI and it doesn't take correct output on some images of apple like on some red, green, yellow. due to hue values I also want to do the same implementation on XILINX software using HDL