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How to unset an image from a picturebox in c#?

I have a picturebox that is intended to have different kinds of images based on the situation. On the other way around, it must have no picture when it's not needed. How to unset an image from that picturebox in c#?

Use the Image property to set the image to display.
Set it to null to display nothing.

You can use pictureBox1.Image = null; to accomplish that.

How to change backcolor of a image?

How to change the BackColor of a transparent image to White using GDI objects without losing the content of the image.
When I tried to change it using the command
this.image.backcolor, the content of the image is lost.

create a bit map for image you want to change and use bitmap.clear(color u want);

First you create a new image with the desired backcolor and the same size as your original image. Then you draw the original image on the new image using Graphics.DrawImage.

Even if you want to use CSS trick to do this, Here is the solution:-
CSS
.reverse{-webkit-filter: invert(100%); filter: invert(100%);}
HTML
<img src="src path" class="reverse">
Same way many other options are available in CSS.
Hope this post will help you :).

Try this,
var newImage = new Bitmap(oldImage.Width, oldImage.Height);
using (var g = Graphics.FromImage(newImage))
{
g.Clear(Color.White);
g.DrawImage(oldImage, new Point(0, 0));
}

Convert PictureBox image to bitmap

I am working with a fingerprint module and am able to capture and display the output in a picture box (C#). Now picture.Image is null even though picturebox displays an image. So I am trying to save the picturebox image as bmp and then assign that bmp to the same picturebox so that Picturebox.image is not null.
Here is the code :
Bitmap bmp = new Bitmap(picFP.width, picFP.height);
picFP.DrawToBitmap(bmp, picFP.ClientRectangle);
bmp.Save("path", Imageformat.bmp);
picFP.image = bmp;
Here bitmap image saved is blank. What can be the problem?

A PictureBox has three layers it can display and PictureBox.DrawToBitmap will put all three things into the Bitmap:
The BackgroundImage
The Image
Any graphics created in or from the Paint event
If your bitmap comes out black then you have none of the three, or the last you have is all black.
From your description it seems as if you can display the image in the PictureBox.
So I assume that you don't display it in the right way, probably you do it like this:
using (Graphics G = picFP.CreateGraphics())
G.DrawImage(yourCapturedImage, ..)
This will not work as it only creates non-persistent graphics. These go away with e.g. each minimize-restore cycle and are not called from the DrawToBitmap call
If you really want to draw it onto the PB's surface use the Paint event! But the more natural choice would be to set the PB's Image directly:
picFP.Image = yourCapturedImage;
Update 1 As you now reveal that you don't display it yourself but simply give the control handle to the external code objNitgen=picFP.Handle; the same applies: It is that Nitgen draws only onto the surface and the result is non-persistent.
In this case the remedy is either
Taking a screenshot of the result and then work from that. Here is a post that shows you how to capture a control via screenshot..
Or you may want to check if Nitgen will draw into a bitmap directly..
For this you should be to pass it not a handle to the PictureBox but to a Bitmap instead:
private void button_Click(object sender, EventArgs e)
{
Bitmap bmp = new Bitmap(picFP.ClientSize.Width, picFP.ClientSize.Height);
Graphics G = Graphics.FromImage(bmp);
IntPtr dc= G.GetHdc();
objNitgen = dc;
objNitgen.capture();
G.ReleaseHdc(dc);
pictureBox1.Image = bmp; // now display..
bmp.Save(yourfilename); // .. and/or save
}
Update 2
You noted in a comment that doing a manual screenshot also does not capture the image; so it seems the control handle is only used to overlay it with the image much like video overlays do; if this is the case I doubt you can get at the image without using other, more fitting Nitgen SDK methods.

C# Remove drawing from PictureBox

I have a PictureBox pic , and an Image img, pic.Image = img
and I draw some rectangles on the Image using
Graphics g = Grpahics.FromImage(pic.Image);
g.DrawRectangle(...);
But at one point, I want to remove the rectangle from the Image,I tried
pic.Image = getOriginalImage();
pic.Refresh();
but the image remains the same(Rectangles are still on top of the Image)
I know there's a method graphics.Clear(Color),but it replace the entire Image with a solid color
How do I remove the drawing only from the PictureBox?
Thanks
Edit:
I already saved the original and when I erase I use the original image

You are overwriting the original image. Save the image locally and clone it into the PictureBox.Image property. Then clone again when you want to erase

Draw the background image again using Graphics.DrawImage() or assign the image again to the Image property. Using a Graphics object in this way is writing directly to the image displayed in the PictureBox and it does not keep separate copies of what is written using a Graphics object and the background Image.

c# picturebox bitmaps

I have a picturebox that upon request, I save the current display to a bitmap.
My question is, how do I then load that same bitmap to the picturebox?
Thanks.
EDIT:
The only relevant code is:
pictureBox1.DrawToBitmap(test1,pictureBox1.ClientRectangle);
The picture box contains graphics that I have written 'freehand' using the mouse. So you can use the mouse to write directly onto the screen when the left mouse is pressed.

You can assign any image to the picture box that you want during run-time. Just set the Image property of the picture box to the picture you want to be displayed.
For example, to display an image in a picture box from a file on your hard drive, you could use something like:
myPicBox.Image = Image.FromFile("C:\savedimage.bmp");
Or, your edit suggests that you have a bitmap object in memory that you want to display in the picture box. In that case, it's a simple matter of assigning that bitmap object to the Image property:
myPicBox.Image = test1; //(where test1 is your bitmap object in memory)
Edit: Just in case you want to save the bitmap object that you created in memory to disk so that you can reload and use it later, check out the Save method of the Bitmap object:
test1.Save("C:\savedimage.bmp", System.Drawing.Imaging.ImageFormat.Bmp);

If I'm not mistaken, the picturebox should have an Image property that you can simply use to assign the Bitmap to.