?
Solved

Convert 24Bit to 32Bit with alpha in C#

Posted on 2009-05-08
5
Medium Priority
?
2,342 Views
Last Modified: 2012-05-06
The Code I wrote below should work. But it will not convert a 24 bit to 32 bit image. It should but apparently Clone doesn't work that way.

Anyone have any alternate solutions?
public static Bitmap SetAlpha(Bitmap Target, int alpha)
        {
 
            /*if (Target.PixelFormat == PixelFormat.Format24bppRgb)
            {
 
                Bitmap newBitmap = new Bitmap(Target.Width, Target.Height, PixelFormat.Format32bppArgb);
 
                BitmapData returnData1 = Target.LockBits(new Rectangle(0, 0, Target.Width, Target.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, Target.PixelFormat);
                BitmapData returnData2 = newBitmap.LockBits(new Rectangle(0, 0, newBitmap.Width, newBitmap.Height), System.Drawing.Imaging.ImageLockMode.WriteOnly, newBitmap.PixelFormat);
 
 
 
            }*/
 
            //Clone the Target to return Bitmap, this will change to pixel format correctly
            Bitmap returnBitmap = Target.Clone(new Rectangle(0, 0, Target.Width, Target.Height), PixelFormat.Format32bppArgb);
 
 
 
            //New fast Code using Lock bits to get and set alpha channel. Don't use Get and Set Pixel it's 10x slower
            BitmapData returnData = returnBitmap.LockBits(new Rectangle(0, 0, returnBitmap.Width, returnBitmap.Height), System.Drawing.Imaging.ImageLockMode.ReadWrite, returnBitmap.PixelFormat);
 
            int PixelSize = 4;
 
            unsafe
            {
 
                for (int y = 0; y < returnData.Height; y++)
                {
                    //Gets the pixelRow for Target Bitmap
                    byte* row = (byte*)returnData.Scan0 + (y * returnData.Stride);
 
                    for (int x = 0; x < returnData.Width; x++)
                    {
                        //Set alpha pixel byte to the same as the mask
 
                        byte oldAlpha = row[x * PixelSize + 3];
                        byte B = row[x * PixelSize + 2];
                        byte G = row[x * PixelSize + 1];
                        byte R = row[x * PixelSize + 0];
                        byte setAlpha = Convert.ToByte(alpha);
 
 
                        //Check for Null pixel
                        if ((R == 0) && (G == 0) && (B == 0) && (oldAlpha < 10)) { R = 254; B = 254; G = 254; setAlpha = oldAlpha; }
                        
 
                        //if (returnBitmap.Height == 290)
                        //{ B = 254; G = 254; R = 254; }
                        //if (alpha > oldAlpha)
                        row[x * PixelSize + 0] = R;
                        row[x * PixelSize + 1] = G;
                        row[x * PixelSize + 2] = B;
                        row[x * PixelSize + 3] = setAlpha;
                    }
 
                }
            }
 
 
            //Restore Bitmap Data Directly back to the bitmap.
            returnBitmap.UnlockBits(returnData);
            
 
            //Dispose of input bitmaps
            Target.Dispose();
 
            return returnBitmap;
        }

Open in new window

0
Comment
Question by:RDdice
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
5 Comments
 
LVL 11

Accepted Solution

by:
anyoneis earned 1500 total points
ID: 24350255
I don't know why the clone doesn't work as you are using it. Try this tweak:

            //Clone the Target to return Bitmap, this will change to pixel format correctly
            Bitmap returnBitmap = new Bitmap(Target);
            returnBitmap = returnBitmap.Clone(new Rectangle(0, 0, Target.Width, Target.Height), PixelFormat.Format32bppArgb);

dwr
0
 
LVL 11

Expert Comment

by:anyoneis
ID: 24350272
0
 
LVL 7

Author Comment

by:RDdice
ID: 24350286
Ya doesn't work. Passing a 24 bit bitmap to it, it doesn't always return a 32 bit for some reason and i'm not sure why. Could be something to do with the bitmaps I'm using.

Bitmap.MakeTransparent Does return a 32 bit in every instance, but of course makes 1 color transparent.
0
 
LVL 11

Expert Comment

by:anyoneis
ID: 24350422
I can't get it to fail, but I am not trying a bunch of different images. Sorry that didn't help (but it was fun playing with it :-)

Are you saying that a given image does not always convert, or that some images never convert with this code?
0
 
LVL 7

Author Closing Comment

by:RDdice
ID: 31579630
Clone works, but not 100% of the time, seems like an internal bug defendant on the target image.
0

Featured Post

The Orion Papers

Are you interested in becoming an AWS Certified Solutions Architect?

Discover a new interactive way of training for the exam.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In my previous two articles we discussed Binary Serialization (http://www.experts-exchange.com/A_4362.html) and XML Serialization (http://www.experts-exchange.com/A_4425.html). In this article we will try to know more about SOAP (Simple Object Acces…
It was really hard time for me to get the understanding of Delegates in C#. I went through many websites and articles but I found them very clumsy. After going through those sites, I noted down the points in a easy way so here I am sharing that unde…
In this brief tutorial Pawel from AdRem Software explains how you can quickly find out which services are running on your network, or what are the IP addresses of servers responsible for each service. Software used is freeware NetCrunch Tools (https…
This is my first video review of Microsoft Bookings, I will be doing a part two with a bit more information, but wanted to get this out to you folks.
Suggested Courses

741 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question