x,y,z to vector offset

Question

I know this may sound stupid but I'm goin crazy with this XD

I'm loading ad image (with ImageMagick) into a 1D vector, so that I have something like:

012345678...
RGBRGBRGB...

Where 0-. Are obviously the indexes of the vector, and R, G, and B are respectively the red byte, green byte, and blue byte. So I have a WIDTHxHEIGHTx3 bytes vector.

Now, let's say I want to access the x,y,z byte, where z is the index of the color, which is the transformation formula to have a linear offset into the vector?

Answer 1

This expression produces an index to color component z at pixel (x,y) :

((y * WIDTH) + x) * 3 + z

Assumptions are:

• Data is placed in row-major order .
• No padding/alignment bytes are used between rows.

Answer 2

假设数据存储为一系列行（不是疯狂的假设），则可以在y*WIDTH*3 + 3*x + z处找到字节x，y， y*WIDTH*3 + 3*x + z