Error while using trackbar to adjust brightness-C#

Hello Experts, I will be getting images into picturebox from two comboboxes dropdown(say 15-20images) by selecting specific folders.I want to adjust their brightness, so when i move the trackbar to adjust brightness the output window fades away and displays a error message.I am working with VS2013-winforms with C#. Thanks in advance,

I have tried with,

 

namespace WindowsFormsApplication1

{

public partial class Form1 : Form

{

Bitmap newbitmap;

ArrayList alist = new ArrayList();

int i = 0;

int filelength = 0;

public Form1()

{

InitializeComponent();

} private void Form1_Load(object sender, EventArgs e)

{

DirectoryInfo di = new DirectoryInfo(@"C:\Users\Arun\Desktop\scanned");

DirectoryInfo[] folders = di.GetDirectories();

comboBox1.DataSource = folders;

}

private void button7_Click(object sender, EventArgs e)

{

if (i + 1 < filelength)

{

pictureBox1.Image = Image.FromFile(alist[i + 1].ToString());

i = i + 1;

pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;

}

}

private void button8_Click(object sender, EventArgs e)

{

if (i - 1 >= 0)

{

pictureBox1.Image = Image.FromFile(alist[i - 1].ToString());

pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;

i = i - 1;

}

}

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)

{

string selected = comboBox1.SelectedItem.ToString();

String fullpath = Path.Combine(@"C:\Users\Arun\Desktop\scanned", selected);

DirectoryInfo di1 = new DirectoryInfo(fullpath);

DirectoryInfo[] folders1 = di1.GetDirectories();

comboBox2.DataSource = folders1;

}

private void button9_Click(object sender, EventArgs e)

{

string selected1 = comboBox1.SelectedItem.ToString();

string selected2 = comboBox2.SelectedItem.ToString();

//Initially load all your image files into the array list when form load first time

System.IO.DirectoryInfo inputDir = new System.IO.DirectoryInfo(Path.Combine(@"C:\Users\Arun\Desktop\scanned", selected1, selected2)); //Source image folder path

try

{

if ((inputDir.Exists))

{

alist.Clear();

//Get Each files

System.IO.FileInfo file = null;

foreach (System.IO.FileInfo eachfile in inputDir.GetFiles())

{

file = eachfile;

if (file.Extension == ".tif")

{

alist.Add(file.FullName); //Add it in array list

//filelength = filelength + 1;

filelength = alist.Count;

}

else if(file.Extension == ".jpg")

{

alist.Add(file.FullName); //Add it in array list

// filelength = filelength + 1;

filelength = alist.Count;

}

}

pictureBox1.Image = Image.FromFile(alist[0].ToString()); //Display intially first image in picture box as sero index file path

pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;

i = 0;

}

}

catch (Exception ex)

{

}

} private void trackBar1_Scroll(object sender, EventArgs e)

{

label2.Text = trackBar1.Value.ToString();

pictureBox1.Image = adjustbrightness (newbitmap, trackBar1.Value);

}

public static Bitmap adjustbrightness(Bitmap image,int value)

{

Bitmap tempbitmap = image;

float finalvalue = (float)value / 255.0f;

Bitmap newbitmap = new Bitmap(tempbitmap.Width, tempbitmap.Height);

Graphics newgraphics = Graphics.FromImage(newbitmap);

float[][] floatcolormatrix = {

new float[] {1,0,0,0,0},

new float[] {0,1,0,0,0},

new float[] {0,0,1,0,0},

new float[] {0,0,0,1,0},

new float[] {finalvalue,finalvalue,finalvalue,1,1}

};

ColorMatrix newcolormatrix = new ColorMatrix(floatcolormatrix);

ImageAttributes attributes = new ImageAttributes();

attributes.SetColorMatrix(newcolormatrix);

newgraphics.DrawImage(tempbitmap, new Rectangle(0, 0, tempbitmap.Width, tempbitmap.Height), 0, 0, tempbitmap.Width, tempbitmap.Height, GraphicsUnit.Pixel, attributes);

attributes.Dispose();

newgraphics.Dispose();

return newbitmap;

}

}

}