what is executed first in c?

I am trying to write a function that applies a sepia filter to the images,

    void sepia(int height, int width, RGBTRIPLE image[height][width])
    {
         for(int i=0; i<height; i++)
         {
            for(int j=0; j<width; j++)
            {
                int r = image[i][j].rgbtRed;
                int g = image[i][j].rgbtGreen;
                int b = image[i][j].rgbtBlue;

                image[i][j].rgbtRed =  round((0.393 * r) + (0.769 * g) + (0.189 * b));
                image[i][j].rgbtGreen =  round((0.349 * r) + (0.686 * g) + (0.168 * b));
                image[i][j].rgbtBlue = round((0.272 * r) + (0.534 * g) + (0.131 * b));


                if(image[i][j].rgbtRed > 255)
                {
                    image[i][j].rgbtRed = 255;
                }

                if(image[i][j].rgbtGreen > 255)
                {
                    image[i][j].rgbtGreen = 255;
                }

                if(image[i][j].rgbtBlue > 255)
                {
                    image[i][j].rgbtBlue = 255;
                }
            }
        }
    }

when I used this code, it does not raise any error, but the if conditions do not work at all, and the resulting image has many creepy pixels.

but when I used intermediate variables like this code below:

    void sepia(int height, int width, RGBTRIPLE image[height][width])
    {
        for(int i=0; i<height; i++)
        {
            for(int j=0; j<width; j++)
            {
                int r = image[i][j].rgbtRed;
                int g = image[i][j].rgbtGreen;
                int b = image[i][j].rgbtBlue;

                int sr =  round((0.393 * r) + (0.769 * g) + (0.189 * b));
                int sg =  round((0.349 * r) + (0.686 * g) + (0.168 * b));
                int sb = round((0.272 * r) + (0.534 * g) + (0.131 * b));


                if(sr > 255)
                {
                    sr = 255;
                }

                if(sg > 255)
                {
                    sg = 255;
                }

                if(sb > 255)
                {
                   sb = 255;
                }

                image[i][j].rgbtRed = sr;
                image[i][j].rgbtGreen = sg;
                image[i][j].rgbtBlue = sb;
            }
         }
     }

the if statements worked perfectly.

my question is what is wrong in the first code that makes the if statements don't work?