Class: Image

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The Image class is declared in mash/image.h.

Contents 1 Representations of an image 2 The Image class 3 How to retrieve the value of a grayscale pixel 4 How to retrieve the value of a RGB pixel

Representations of an image

The Image class can store several different representations of a single image. Currently, the following are supported:

• RGB: Color image, each pixel is stored in RGB (24 bits) format
• Grayscale: Grayscale image, each pixel is stored on 8 bits

The Image class

Here are the relevant part of the declaration of the class. See below for usage examples

//--------------------------------------------------------------------------
// Represents a byte
//--------------------------------------------------------------------------
typedef unsigned char byte_t;
 
 
//--------------------------------------------------------------------------
// Represents a RGB pixel 
//--------------------------------------------------------------------------
struct RGBPixel_t
{
    byte_t r;
    byte_t g;
    byte_t b;
};
 
 
class Image
{
    ...
 
public:
    //----------------------------------------------------------------------
    // Returns the width of the image, in pixels 
    //----------------------------------------------------------------------
    unsigned int width() const;
 
    //----------------------------------------------------------------------
    // Returns the height of the image, in pixels 
    //----------------------------------------------------------------------
    unsigned int height() const;
 
    //----------------------------------------------------------------------
    // Returns a pointer to the pixels in RGB (24 bits) format
    //----------------------------------------------------------------------
    RGBPixel_t* rgbBuffer() const;
 
    //----------------------------------------------------------------------
    // Returns an array of pointers to the lines of the RGB (24 bits) pixel
    // buffer
    //----------------------------------------------------------------------
    RGBPixel_t** rgbLines() const;
 
    //----------------------------------------------------------------------
    // Returns a pointer to the pixels in grayscale (8 bits) format
    //----------------------------------------------------------------------
    byte_t* grayBuffer() const;
 
    //----------------------------------------------------------------------
    // Returns an array of pointers to the lines of the grayscale pixel
    // buffer
    //----------------------------------------------------------------------
    byte_t** grayLines() const;
 
    ....
};

How to retrieve the value of a grayscale pixel

There's two ways to access the pixels:

• Use a one-dimensional array of <image width>x<image height> pixels. This forces you to compute the offset of the desired pixel like that:

// Access the grayscale pixel at (x, y)
byte_t* pBuffer = image->grayBuffer();
byte_t mypixel = pBuffer[y * image->width() + x];

• Use an array of pointers to the lines of the image. This allows you to write a shorter code like:

// Access the grayscale pixel at (x, y)
byte_t** pLines = image->grayLines();
byte_t mypixel = pLines[y][x];

How to retrieve the value of a RGB pixel

Like for the grayscale case above, there's two ways to access the pixels:

• Use a one-dimensional array of <image width>x<image height> pixels:

// Access the RGB pixel at (x, y)
RGBPixel_t* pBuffer = image->rgbBuffer();
RGBPixel_t mypixel = pBuffer[y * image->width() + x];

• Use an array of pointers to the lines of the image:

// Access the RGB pixel at (x, y)
RGBPixel_t** pLines = image->rgbLines();
RGBPixel_t mypixel = pLines[y][x];