用户使用seekg从像素选择的C ++ RGB值

Question

I need to create a program that loads a .raw image (generic 100x100 image), asks the user to select an (x, y) coordinate within the range, and display the red, green, and blue values for said pixel using the seekg function. I'm at a loss as to how to get the rgb values from the pixel. I've gone through every chapter of the textbook that we've covered so far, and there is nothing about retreiving rgb values.

The code asking for the coordinates and giving an error message if outside the range is working fine. Only when I try to come up with the code for using seekg/getting the rgb values am I running in to trouble. I've looked at different questions on the site, and there is good information here, but I've not see any answers using seekg in order to get the rgb values.

I'm not looking for anyone to produce the code for me, just looking for some guidance and a push in the right direction.

loc = (y * 100 + x) * 3;  // code given by professor with 100 being the width of the image
imageRaw.seekg(loc, ios::beg);

And then I'm at a loss.

Any help would be greatly appreciated.

Answer 1

From there, you probably need to read three bytes, which will represent the red, green, and blue values. You haven't told us enough to be sure of the order; green is almost always in the middle, but RGB and BGR are both fairly common.

From a practical viewpoint, for a picture of this size you don't normally want to use seekg at all though. You'd read the entire image into memory, and lookup the values in the vector (or array, if you insist) that stores the data.