[?] Convert an rgb image into grayscale using For function and matrix?

Questions
1

Hi, I’m new at image processing with mathematica and I need to convert a rgb image to a grayscale one using For function. I’ve tried this but I don’t know how to do it:

Captura.PNG.jpg
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2

Edward,

Why do you use For[] function. I strongly discourage you doing so. In Wolfram Language conversion from RGB to "Grayscale" is easier than pronouncing it :slight_smile:

i  =  Import["ExampleData/coneflower.jpg"]; 
ImageColorSpace[i]

(* ==> "RGB" *)

iNew  =  ColorConvert[i,  "Grayscale"]; 
ImageColorSpace[iNew]

(* ==> "Grayscale" *)
3

I know I can do it in one step using Wolfram Language conversion but I was asked to do it with For function for a
task

4

This is the easiest way I can think of right now:

rgbToGrayScale[imageIn_Image, factor_ : 1] :=
	Module[{res, w, h, i, j, r, g, b, data, image = imageIn},
		res = 
		        If [StringMatchQ[ImageColorSpace[image], "RGB"] && ImageChannels[image] === 3,
			            If[(Interleaving /. Options[image, Interleaving]),
			        	        image = Image[image, Interleaving -> True];
			            ];
			
			            data = ImageData[image];
			
			            {w, h} = ImageDimensions[image];
			            res = ConstantArray[ConstantArray[0, w], h];
			
			            For[i = 1, i <= w, ++ i , 
				                For[j = 1, j <= h, ++ j,
				        	        {r, g, b} = data[[j, i]];
				               	        res[[j, i]] = Mean[{r, g, b}^factor];
				                ];
			            ];
			
			            Image[res]
			            ,
			            image
		        ];
		
		Return[res];
	];

You can use it as follows:

rgbToGrayScale[i]
rgbToGrayScale[i, 2]
rgbToGrayScale[i, 1.34]

p.s. Algebra, Computer-Based Maths, 3D Printing have nothing to do with your question. Please consider removing them.