How do I pass C# Bitmap images as MWArrays into my .NET object created with MATLAB Builder for .NET 2.0?

I have the following MATLAB code that performs edge detection on a matrix of image data:

function iprocess(A)

BW=edge(A, 'sobel');

imshow(BW);

I invoke this function in MATLAB as follows:

A = imread('C:\lena.bmp');

iprocess(A)

I am generating a .NET component from iprocess.m using MATLAB Builder for .NET and want to know how to pass a Bitmap image created in C# to this function. This is how I create a Bitmap image in my C# application:

int width = 256;

int height = 256;

Image image = Image.FromFile("C:\\lena.bmp");

Bitmap bitmap = new Bitmap(image, new Size(width, height));

Answer 1

[MathWorks Support Team]

The Bitmap data must be converted into one of the supported datatypes that are derived from MWArray. The first step is to create a native C# double array containing the image data:

//Get image dimensions

int width = bitmap.Width;

int height = bitmap.Height;

//Declare the double array of grayscale values to be read from "bitmap"

double[,] bnew = new double[width, height];

//Loop to read the data from the Bitmap image into the double array

int i, j;

for (i = 0; i < width; i++)

{

     for (j = 0; j < height; j++)

     {

        Color pixelColor = bitmap.GetPixel(i, j);

        double b = pixelColor.GetBrightness(); //the Brightness component

        //Note that rows in C# correspond to columns in MWarray

        bnew.SetValue(b,i, j);

     }

}

And pass it into the .NET object after typecasting it to an MWNumericArray:

//Instantiate the .NET object

iprocessclass ip= new iprocessclass();

//typecast the double[] data into a MWNumericArray and pass it into the .NET method

ip.iprocess((MWNumericArray) bnew);

For more information about the MWArray API refer to the MATLAB documentation:

web([docroot,'/toolbox/dotnetbuilder/MWArrayAPI/HTML/index.html'])