Converting RGB Images to Gray-Scale by the Weighted Average Method, based on Shift-and-Add Technique on the Combination of Color Components for Reducing the Computational Units and Errors in FPGA

Subject Areas : Field programmable logic gate array (FPGA)

Mahdi Ajamin Hamednai ¹ , Payam Sanaee ^{2 *}

1 - Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2 - Digital Processing and Machine Vision Research Center, Najafabad Branch, Islamic Azad University, Najafabad, Iran

Received: 2022-12-04 Accepted : 2023-04-01 Published : 2025-09-23

Keywords: Computational complexity, fixed-point, field programmable gate arrays, image processing, RGB (red-green-blue) to gray-scale,

Abstract :

Converting RGB (red-green-blue) images to gray-scale is one of the important and fundamental issues in the field of image processing, so many algorithms have been developed to achieve this purpose. These algorithms are used in the most of the machine vision applications pre-processing unit to recognize face, target and objects. In the nearly all image recognition processes, the frame rate of the images which are applied to the system through the digital cameras, is too high; Therefore, in order to achieve real-time processing, the speed of algorithm calculations must be increased. Field programmable gate arrays (FPGA) chips are one of the choices to process algorithms by hardware rapidly. The advantages of these chips are the possibility of hardware implementation of procedures by concurrent and parallel processing algorithms and fully combinational logic circuits. In this research to reduce the calculation error, we used a fixed-point system, and we have a tradeoff between the accuracy and the used logic-blocks. This will help us to manage the hardware resources perfectly. In this article, we design and compare different methods to convert color image to gray on inexpensive FPGA chip. By using the combining color components method with fixed-point calculations (the fractional part of the image components coefficients are 8/15 bits, and in the calculations, the fractional part of numbers 8 bits), the mean square error (MSE) index for the Lenna 512×512 grayscale image was 0.0184 and 105 logic block (LB) units were used to implement the corresponding hardware.

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