change brightness of image realtime

jimmy naik

hello guys..i want to change the brightness of the checked images that i have added in the list view in real time using trackbar i.e as i slide the trackbar i want the brightness to be changed simultaneously .can any one help me over here pls

//this is code where i loop through checked images in listview

for (int i = 0; i < listView1.Items.Count; i++)
            {
                if (listView1.Items[i].Checked)
                {
                    Bitmap img = (Bitmap)imageList.Images[i];

                    if (brighten(img, trackBar1.Value))
                    { this.Invalidate(); }
                }
            }

//this is the code to change brightness of the image

public bool brighten(Bitmap b, int trk)
        {
            if (trk < -255 || trk > 255)
                return false;
            BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);

            int stride = bmData.Stride;
            System.IntPtr Scan0 = bmData.Scan0;

            int nVal = 0;

            unsafe
            {
                byte* p = (byte*)(void*)Scan0;

                int nOffset = stride - b.Width * 3;
                int nWidth = b.Width * 3;

                for (int y = 0; y < b.Height; ++y)
                {
                    for (int x = 0; x < nWidth; ++x)
                    {
                        nVal = (int)(p[0] + trk);

                        if (nVal < 0) nVal = 0;
                        if (nVal > 255) nVal = 255;

                        p[0] = (byte)nVal;

                        ++p;
                    }
                    p += nOffset;
                }
            }

            b.UnlockBits(bmData);

            return true;
        }
i know this logic is wronge ..m still learning c # .pls someone help me on how to implement this properly.
i hope i was clear on my doubt.

thnks

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

none16y ago
Accepted answer
there`s a few options...   (that with unsafe block it`s a middle one)
If you want the fastest methode try to change ColorMatrix

public static Bitmap AdjustBrightness(Bitmap Image, int Value)
        {
            System.Drawing.Bitmap TempBitmap = Image;
            float FinalValue = (float)Value / 255.0f;
            System.Drawing.Bitmap NewBitmap = new System.Drawing.Bitmap(TempBitmap.Width, TempBitmap.Height);
            System.Drawing.Graphics NewGraphics = System.Drawing.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}
                };

            System.Drawing.Imaging.ColorMatrix NewColorMatrix = newSystem.Drawing.Imaging.ColorMatrix(FloatColorMatrix);
            System.Drawing.Imaging.ImageAttributes Attributes = newSystem.Drawing.Imaging.ImageAttributes();
            Attributes.SetColorMatrix(NewColorMatrix);
            NewGraphics.DrawImage(TempBitmap, new System.Drawing.Rectangle(0, 0, TempBitmap.Width, TempBitmap.Height), 0, 0, TempBitmap.Width, TempBitmap.Height, System.Drawing.GraphicsUnit.Pixel, Attributes);
            Attributes.Dispose();
            NewGraphics.Dispose();
            return NewBitmap;
        }
paul daniel16y ago
Refer this link

http://www.codeproject.com/KB/GDI-plus/csharpgraphicfilters11.aspx
Hiren Soni16y ago
private static Bitmap brightness(Bitmap b, int brightnessvalue )

{

Bitmap bmap = b;
Color c;

for (int i = 0; i < bmap.Width; i++)
{
for (int j = 0; j < bmap.Height; j++)
{

c = bmap.GetPixel(i, j);

int cR = c.R + brightnessvalue;
int cG = c.G + brightnessvalue;
int cB = c.B + brightnessvalue;

if (cR < 0) cR = 1;
if (cR > 255) cR = 255;

if (cG < 0) cG = 1;
if (cG > 255) cG = 255;
if (cB < 0) cB = 1;
if (cB > 255) cB = 255;

bmap.SetPixel(i, j, Color.FromArgb(cR, cG, cB));
}

return bmap;

}

// here is code for brightness use as you wish in your project
// dont 4get to accept answer