Some image operations in C#.NET

Flip Image

Using the Image.RotateFlip method, we can rotate the image by 90/180/270-degrees or flip the image horizontally or vertically.

The parameter of RotateFlip is System.Drawing.RotateFlipType, which specifies the type of rotation and flip to apply to the image.

Code Snippet:

//Specifies a 180-degree rotation without flipping
pictureBox1.Image.RotateFlip(RotateFlipType.Rotate180FlipNone);




//Specifies no rotation followed by a horizontal flip
pictureBox1.Image.RotateFlip(RotateFlipType.RotateNoneFlipX);



//Specifies a 90-degree rotation followed by a horizontal and vertical flip pictureBox1.Image.RotateFlip(RotateFlipType.Rotate90FlipXY);







Join Two Images

Bitmap bitmap = new Bitmap(image1.Width + image2.Width, Math.Max(image1.Height, image2.Height));

    using (Graphics g = Graphics.FromImage(bitmap))

    {

        g.DrawImage(image1, 0, 0);

        g.DrawImage(image2, image1.Width, 0);

    }







Convert Bitmap to byte[] and vice-versa using C#

Here is the function to convert bitmap to byte[] in C# using ImageConverter class. ImageConverter class is present in System.Drawing.dll.

public static byte[] BitmapToByteArray(Bitmap bitmap)
{            
     ImageConverter converter = new ImageConverter();            
     return (byte[])converter.ConvertTo(bitmap, typeof(byte[]));
} 

Here is the code to convert byte[] to bitmap in C#

public static Bitmap ByteArrayToBitMap(byte[] imageData)        
{            
    Bitmap bmp;            
    using (var ms = new MemoryStream(imageData))
    {            
        bmp = new Bitmap(ms);
    }                       
return bmp;        
}

Create Thumbnail of Image using C#

Thumbnail is the reduced sized image of the given image. We can use thumbnail where we need to display large number of images. Using  GetThumbnailImage method we can create thumbnail for any give image.

The basic syntax used to create thumbnail using C# is -

Image img = Image1.GetThumbnailImage(thumbnail.Height, thumbnail.Width, Image.GetThumbnailImageAbort callback, IntPtr callbackData)


Here is the example -


Bitmap testimage = (Bitmap)TestApplication.Properties.Resources.testimage.GetThumbnailImage(450,550, null, IntPtr.Zero);

Pass byte array from C# to C++                          

If you want to pass a byte array to native DLL as parameter, you can use the Intptr to do this, please check the demo below.

//C++ API code:

TestDLL_API  void TestArrayPara(BYTE * pArray, int nSize)

{

        for (int i=0; i<nSize; i++)

        printf("%d\n", pArray[i]);

}

//C# code:

class TestClass

    {

        [DllImport(@"TestDll.dll")]

        public static extern void TestArrayPara(IntPtr pArray, int nSize);

        public static void Test()

        {

            byte[] array = new byte[16];

             for (int i = 0; i < 16; i++)

            {

                array[i] = (byte)(i + 97);

            }

            int size = Marshal.SizeOf(array[0]) * array.Length;

            IntPtr pnt = Marshal.AllocHGlobal(size);

           try

            {

                // Copy the array to unmanaged memory.

                Marshal.Copy(array, 0, pnt, array.Length);               

            }

            finally

            {

                // Free the unmanaged memory.

               // Marshal.FreeHGlobal(pnt);

            }

            TestArrayPara(pnt, array.Length);

            Marshal.FreeHGlobal(pnt);

            Console.WriteLine("End of app");

        }

}

Return char array from C++ to c#

//C++ code

extern "C" __declspec(dllexport) int* test() 

{

    int * arr=new int[4];

    arr[0]=1;

    arr[1]=2;

    arr[2]=3;

    arr[3]=4;

        return arr;}

extern "C" __declspec(dllexport) int ReleaseMemory(int* pArray){

    delete[] pArray;

    return 0;}

//C# code

[DllImport("C:\\Devs\\C++\\Projects\\Interop\\InteropTestApp\\Debug\\InteropTestApp.dll")]

        public static extern IntPtr test();

        [DllImport("C:\\Devs\\C++\\Projects\\Interop\\InteropTestApp\\Debug\\InteropTestApp.dll", CallingConvention = CallingConvention.Cdecl)]

        public static extern int ReleaseMemory(IntPtr ptr);

        static void Main(string[] args)

        {

            IntPtr ptr = test();

            int[] result = new int[4];

            Marshal.Copy(ptr, result, 0, 4);

            ReleaseMemory(ptr);

            Console.ReadKey();

        }

    }