Image Data Structure

T ## Image buffer model

Data is stored in an unsigned char* buffer in row-order of a (\(width * height * N\)) size.

• The image has height rows and width columns.
• Each pixel has N components.
• In this project, N = 3 for RGB.
• Data is row-major, from top-left to bottom-right.

The buffer size is:

width * height * N

To manipulate image, you will have to use an ’unsigned char *’ which points to the pixel data. The pixel data consists of HEIGHT lines of WIDTH pixels, with each pixel consisting of N components. In our case, we will use N = 3 for RGB components. The first pixel pointed to is top-left-most in the image.

Data is stored flat

IO functions

int read_image_data(const char *filename, unsigned char **data, int *width, int *height, int *nbChannels);
int write_image_data(const char *filename, unsigned char *data, int width, int height);

Parameters:

• filename: image file path
• data: pixel buffer
• width: image width
• height: image height
• nbChannels: number of channels

Pixel helper structure

At the end of Milestone 1, you should introduce a helper structure:

typedef struct _pixelRGB {
  unsigned char R;
  unsigned char G;
  unsigned char B;
} pixelRGB;

This structure simplifies component-level access and supports helper functions such as getPixel(x, y).

Index formula

For pixel at (x, y) with channel count n, the starting index in data is:

(y * width + x) * n

Then channels are:

• R: data[idx]
• G: data[idx + 1]
• B: data[idx + 2]