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How to create transparent controls in Windows Forms when controls are layered

I am trying to implement a "Fillable Form" in which editable text fields appear over top of an image of a pre-preprinted form for a dot matrix printer. (using c# and Windows Forms and targeting .Net 2.0) My first idea was to use the image as the Windows Form background, but it looked horrible when scrolling and also did not scroll properly with the content.
My next attempt was to create a fixed-size window with a panel that overflows the bounds of the window (for scrolling purposes.) I added a PictureBox to the panel, and added my textboxes on top of it. This works fine, except that TextBoxes do not support transparency, so I tried several methods to make the TextBoxes transparent. One approach was to use an odd background color and a transparency key. Another, described in the following links, was to create a derived class that allows transparency:
Transparency for windows forms textbox
TextBox with a Transparent Background
Neither method works, because as I have come to find out, "transparency" in Windows Forms just means that the background of the window is painted onto the control background. Since the PictureBox is positioned between the Window background and the TextBox, it gives the appearance that the TextBox is not transparent, but simply has a background color equal to the background color of the Window. With the transparency key approach, the entire application becomes transparent so that you can see Visual Studio in the background, which is not what I want. So now I am trying to implement a class that derives from TextBox and overrides either OnPaint or OnPaintBackground to paint the appropriate part of the PictureBox image onto the control background to give the illusion of transparency as described in the following link:
How to create a transparent control which works when on top of other controls?
First of all, I can't get it working (I have tried various things, and either get a completely black control, or just a standard label background), and second of all, I get intermittent ArgumentExceptions from the DrawToBitmap method that have the cryptic message "Additional information: targetBounds." Based on the following link from MSDN, I believe that this is because the bitmap is too large - in either event it seems inefficient to capture the whole form image here because I really just want a tiny piece of it.
https://msdn.microsoft.com/en-us/library/system.windows.forms.control.drawtobitmap(v=vs.100).aspx
Here is my latest attempt. Can somebody please help me with the OnPaintBackground implementation or suggest a different approach? Thanks in advance!
public partial class TransparentTextbox : TextBox
{
public TransparentTextbox()
{
InitializeComponent();
SetStyle(ControlStyles.OptimizedDoubleBuffer |
ControlStyles.AllPaintingInWmPaint |
ControlStyles.ResizeRedraw |
ControlStyles.UserPaint, true);
}
protected override void OnPaintBackground(PaintEventArgs e)
{
//base.OnPaintBackground(e); // not sure whether I need this
if (Parent != null)
{
foreach (Control c in Parent.Controls)
{
if (c.GetType() == typeof(PictureBox))
{
PictureBox formImg = (PictureBox)c;
Bitmap bitmap = new Bitmap(formImg.Width, formImg.Height);
formImg.DrawToBitmap(bitmap, formImg.Bounds);
e.Graphics.DrawImage(bitmap, -Left, -Top);
break;
}
}
Debug.WriteLine(Name + " didn't find the PictureBox.");
}
}
}
NOTE: This has been tagged as a duplicate, but I referenced the "duplicate question" in my original post, and explained why it was not working. That solution only works if the TextBox sits directly over the Window - if another control (such as my Panel and PictureBox) sit between the window and the TextBox, then .Net draws the Window background onto the TextBox background, effectively making its background look gray, not transparent.

I think I have finally gotten to the bottom of this. I added a Bitmap variable to my class, and when I instantiate the textboxes, I am setting it to contain just the portion of the form image that sits behind the control. Then I overload OnPaintBackground to display the Bitmap, and I overload OnPaint to manually draw the text string. Here is the updated version of my TransparentTextbox class:
public partial class TransparentTextbox : TextBox
{
public Bitmap BgBitmap { get; set; }
public TransparentTextbox()
{
InitializeComponent();
SetStyle(ControlStyles.OptimizedDoubleBuffer |
ControlStyles.AllPaintingInWmPaint |
ControlStyles.ResizeRedraw |
ControlStyles.UserPaint, true);
}
protected override void OnPaint(PaintEventArgs e)
{
e.Graphics.DrawString(this.Text, this.Font, Brushes.Black, new PointF(0.0F, 0.0F));
}
protected override void OnPaintBackground(PaintEventArgs e)
{
e.Graphics.DrawImage(BgBitmap, 0, 0);
}
}
... and here is the relevant part of how I instantiate:
Bitmap bgImage = (Bitmap)Bitmap.FromStream(Document.FormImage);
PictureBox pb = new PictureBox();
pb.Image = bgImage;
pb.Size = pb.Image.Size;
pb.Top = 0;
pb.Left = 0;
panel1.Controls.Add(pb);
foreach (FormField field in Document.FormFields)
{
TransparentTextbox tb = new TransparentTextbox();
tb.Width = (int)Math.Ceiling(field.MaxLineWidth * 96.0);
tb.Height = 22;
tb.Font = new Font("Courier", 12);
tb.BorderStyle = BorderStyle.None;
tb.Text = "Super Neat!";
tb.TextChanged += tb_TextChanged;
tb.Left = (int)Math.Ceiling(field.XValue * 96.0);
tb.Top = (int)Math.Ceiling(field.YValue * 96.0);
tb.Visible = true;
Bitmap b = new Bitmap(tb.Width, tb.Height);
using (Graphics g = Graphics.FromImage(b))
{
g.DrawImage(bgImage, new Rectangle(0, 0, b.Width, b.Height), tb.Bounds, GraphicsUnit.Pixel);
tb.BgBitmap = b;
}
panel1.Controls.Add(tb);
}
I still need to work on how the text looks when I highlight it, and other things like that, but I feel like I am on the right track. +1 to Reza Aghaei and Mangist for commenting with other viable solutions!

C# Panel is flickering. When I try CreateParams, the situation is much worse

The title pretty much says it. I have a panel inside of my form. I have lots of Shapes in the panel that bounce off of each other. The more shapes I have the worse the flickering is. After searching on this site for awhile I added this to the constructor
this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint
| ControlStyles.DoubleBuffer, true);
Then I found I should also add this
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000; // Turn on WS_EX_COMPOSITED (child control double-buffering)
return cp;
}
}
After I added this the screen flickered MUCH worse. It's not even fair to say it flickered. Most of the time it was just blank and every once in a while the shapes would flash briefly. My code to paint the shapes looks like this.
pnl.Refresh();
Graphics g = pnl.CreateGraphics();
for(int i = 0; i < numOfShapes; i++)
{
Rectangle myRect = shapeList[i];
g.FillRectangle(new SolidBrush(Color.Black), myRect);
}
edit:
I don't know why I can't get the last bit of code to look right. Sorry about that. I'm just refreshing the panel then looping through an array of rectangles and painting them to the panel

C#, how to make a picture background transparent?

I have a picturebox with a png in it. Yet even when I set the BackColor to Transparent, it is not transparent. Any ideas what might be wrong? :)
Thanks!

I have also faced the problem regarding transparent pictures.
you have to Draw it through code.
See my question A PictureBox Problem
EDIT:
In paint event (Control containing Background Image)
write this
//If added your image in project's resources get from there OR your Image location
Image img = yourNamespace.Properties.Resources.yourPicture;
e.Graphics.DrawImage(img,50,50,100,100);

Your PNG file should also have the transparent background. This is can be done while creating the image(png) files.

You really have to draw it through code. Place a pictureBox on your form, set sizeMode and docking as you like. Then you may fire the following function on the pictureBox's PAINT event:
public void LogoDrawTransparent(PaintEventArgs e)
{
// Create a Bitmap object from an image file.
Image myImg;
Bitmap myBitmap;
try
{
myImg = cls_convertImagesByte.GetImageFromByte(newImg);
myBitmap = new Bitmap(myImg); // #"C:\Temp\imgSwacaa.jpg");
// Get the color of a background pixel.
Color backColor = myBitmap.GetPixel(0, 0); // GetPixel(1, 1);
Color backColorGray = Color.Gray;
Color backColorGrayLight = Color.LightGray;
Color backColorWhiteSmoke = Color.WhiteSmoke;
Color backColorWhite = Color.White;
Color backColorWheat = Color.Wheat;
// Make backColor transparent for myBitmap.
myBitmap.MakeTransparent(backColor);
// OPTIONALLY, you may make any other "suspicious" back color transparent (usually gray, light gray or whitesmoke)
myBitmap.MakeTransparent(backColorGray);
myBitmap.MakeTransparent(backColorGrayLight);
myBitmap.MakeTransparent(backColorWhiteSmoke);
// Draw myBitmap to the screen.
e.Graphics.DrawImage(myBitmap, 0, 0, pictureBox1.Width, pictureBox1.Height); //myBitmap.Width, myBitmap.Height);
}
catch
{
try { pictureBox1.Image = cls_convertImagesByte.GetImageFromByte(newImg); }
catch { } //must do something
}
}
This is my class that is referenced in the above function:
class cls_convertImagesByte
{
public static Image GetImageFromByte(byte[] byteArrayIn)
{
MemoryStream ms = new MemoryStream(byteArrayIn);
Image returnImage = Image.FromStream(ms);
return returnImage;
}
public static byte[] GetByteArrayFromImage(System.Drawing.Image imageIn)
{
MemoryStream ms = new MemoryStream();
imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
return ms.ToArray();
}
}
Thanks. chagbert.

From what I learned I can't do it within a windows form, as it doesn't have layers for the images. So guess will have to make it as WPF. :)

How did you create the background? Is that set by setting the Form.BackgroundImage?
If that background (the paper like image) is a container control, the transparency should just work.
However, If you are placing two PictureBox objects on top of eachother this doesn't work. The transparent area takes on the color of its parent object. If you have two PictureBox objects they both will have the Form as their parent. If this is your situation, it can be solved by setting the transparent image's Parent property to be the background image.
private void Form1_Load(object sender, EventArgs e)
{
transparentPictureBox.Parent = backgroundPictureBox;
}
When changing the Parent property, the Location of the tranparentPictureBox will become relative to its new parent. You'd have to subtract the x and y coordinates of the background image from the transparent image. See my answer on A PictureBox Question for an example with a screen shot.
AFAIK, you can not set the Parent in the Designer, only in code. Therefore, the Designer will still not show a transparent image, but at runtime it should.
The same problem occurs if you place a transparent Label on top of a PictureBox object.

Set datagrid view background to transparent

I tried to set the background color of a data grid view to be "transparent" from properties but it it said "not a valid property".
How can I do it?

I did this solution to a specific problem (when the grid was contained in a form with background image) with simples modifications you can adapt it to create a generic transparent Grid, just ask if the parent have background image, else just use the parent backcolor to paint your grid, and that is all.
You must inherit from DataGridView and override the PaintBackground method like this:
protected override void PaintBackground(Graphics graphics, Rectangle clipBounds, Rectangle gridBounds)
{
base.PaintBackground(graphics, clipBounds, gridBounds);
Rectangle rectSource = new Rectangle(this.Location.X, this.Location.Y, this.Width, this.Height);
Rectangle rectDest = new Rectangle(0, 0, rectSource.Width, rectSource.Height);
Bitmap b = new Bitmap(Parent.ClientRectangle.Width, Parent.ClientRectangle.Height);
Graphics.FromImage(b).DrawImage(this.Parent.BackgroundImage, Parent.ClientRectangle);
graphics.DrawImage(b, rectDest, rectSource, GraphicsUnit.Pixel);
SetCellsTransparent();
}
public void SetCellsTransparent()
{
this.EnableHeadersVisualStyles = false;
this.ColumnHeadersDefaultCellStyle.BackColor = Color.Transparent;
this.RowHeadersDefaultCellStyle.BackColor = Color.Transparent;
foreach (DataGridViewColumn col in this.Columns)
{
col.DefaultCellStyle.BackColor = Color.Transparent;
col.DefaultCellStyle.SelectionBackColor = Color.Transparent;
}
}

i did this with Deumber's solution and it works, but causes some troubles that i avoided by adding small improvements:
A. scrolling the DGV messes up the background. solution: put this somewhere:
public partial class main : Form
{
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000;
return cp;
}
}
}
the background will still scroll, but be corrected immediately after each scroll step. it's noticeable, but was acceptable for me. does anyone know a better solution to support scrolling with this?
B. the designer has troubles using it. solution:
protected override void PaintBackground(Graphics graphics, Rectangle clipBounds, Rectangle gridBounds)
{
base.PaintBackground(graphics, clipBounds, gridBounds);
if (main.ActiveForm != null && this.Parent.BackgroundImage != null)
{
Rectangle rectSource = new Rectangle(this.Location.X, this.Location.Y, this.Width, this.Height);
Rectangle rectDest = new Rectangle(-3, 3, rectSource.Width, rectSource.Height);
Bitmap b = new Bitmap(Parent.ClientRectangle.Width, Parent.ClientRectangle.Height);
Graphics.FromImage(b).DrawImage(this.Parent.BackgroundImage, Parent.ClientRectangle);
graphics.DrawImage(b, rectDest, rectSource, GraphicsUnit.Pixel);
SetCellsTransparent();
}
}
now the designer treats it just like a DGV. it will fail if you ever want to draw the DGV while you have no ActiveForm, but that's not the case usually. it's also possible to just keep the if-line while you might still want to use the designer, and delete it for the release.

Having a transparent color in the DataGridView BackGroundColor property is not possible.
So I decided to sync this property with the parent's BackColor. The good old databinding feature of WinForms is very good at this :
myDataGridView.DataBindings.Add(nameof(DataGrid.BackgroundColor),
this,
nameof(Control.BackColor));
Just after InitializeComponents();
I know this is pretty old, but this works very well.

You need to set all the rows and columns to transparent. Easier way is:
for (int y = 0; y < gridName.Rows[x].Cells.Count; y++)
{
yourGridName.Rows[x].Cells[y].Style.BackColor =
System.Drawing.Color.Transparent;
}

Set datagridview's backcolor same with the form's color. To do this, select datagridview: go to Properties -> RowTemplate -> DefaultCellStyle -> BackColor and choose the color of your form.

Drawing a transparent button

I'm trying to create a transparent button in C# (.NET 3.5 SP1) to use in my WinForms application. I've tried everything to get the button to be transparent (it should show the gradient background underneath the button) but it's just not working.
Here is the code I'm using:
public class ImageButton : ButtonBase, IButtonControl
{
public ImageButton()
{
this.SetStyle(
ControlStyles.SupportsTransparentBackColor |
ControlStyles.OptimizedDoubleBuffer |
ControlStyles.AllPaintingInWmPaint |
ControlStyles.ResizeRedraw |
ControlStyles.UserPaint, true);
this.BackColor = Color.Transparent;
}
protected override void OnPaint(PaintEventArgs pevent)
{
Graphics g = pevent.Graphics;
g.FillRectangle(Brushes.Transparent, this.ClientRectangle);
g.DrawRectangle(Pens.Black, this.ClientRectangle);
}
// rest of class here...
}
The problem is that the button seems to be grabbing random UI memory from somewhere and filling itself with some buffer from Visual Studio's UI (when in design mode). At runtime it's grabbing some zero'd buffer and is completely black.
My ultimate goal is to paint an image on an invisible button instead of the rectangle. The concept should stay the same however. When the user hovers over the button then a button-type shape is drawn.
Any ideas?
EDIT: Thanks everybody, the following worked for me:
public class ImageButton : Control, IButtonControl
{
public ImageButton()
{
SetStyle(ControlStyles.SupportsTransparentBackColor, true);
SetStyle(ControlStyles.Opaque, true);
SetStyle(ControlStyles.ResizeRedraw, true);
this.BackColor = Color.Transparent;
}
protected override void OnPaint(PaintEventArgs pevent)
{
Graphics g = pevent.Graphics;
g.DrawRectangle(Pens.Black, this.ClientRectangle);
}
protected override void OnPaintBackground(PaintEventArgs pevent)
{
// don't call the base class
//base.OnPaintBackground(pevent);
}
protected override CreateParams CreateParams
{
get
{
const int WS_EX_TRANSPARENT = 0x20;
CreateParams cp = base.CreateParams;
cp.ExStyle |= WS_EX_TRANSPARENT;
return cp;
}
}
// rest of class here...
}

WinForms (and underlying User32) does not support transparency at all. WinForms however can simulate transparency by using control style you provide - SupportsTransparentBackColor, but in this case all that "transparent" control does, it to allow drawing parent its background.
ButtonBase uses some windows styles that prevent working this mechanism. I see two solutions: one is to derive your control from Control (instead of ButtonBase), and second is to use Parent's DrawToBitmap to get background under your button, and then draw this image in OnPaint.

In winforms there are some tricks to allow a control having its background correctly painted when using transparency. You can add this code to the OnPaint or OnPaintBackground to get the controls you have in the background being painted:
if (this.Parent != null)
{
GraphicsContainer cstate = pevent.Graphics.BeginContainer();
pevent.Graphics.TranslateTransform(-this.Left, -this.Top);
Rectangle clip = pevent.ClipRectangle;
clip.Offset(this.Left, this.Top);
PaintEventArgs pe = new PaintEventArgs(pevent.Graphics, clip);
//paint the container's bg
InvokePaintBackground(this.Parent, pe);
//paints the container fg
InvokePaint(this.Parent, pe);
//restores graphics to its original state
pevent.Graphics.EndContainer(cstate);
}
else
base.OnPaintBackground(pevent); // or base.OnPaint(pevent);...

I'm not sure ButtonBase supports transparency... have you checked that out?
I've written a number of transparent controls, but I have always inherited from Control or UserControl.
When you want to block out a control painting it's background - you should override OnPaintBackground instead of OnPaint and not call the base class.
Filling a rectangle with Brushes.Transparent is funny though - you're painting with an invisible color over what's aready there. Or to put it another way: it does nothing!

I know this question is old, but if someone doesn't want to create a control to do this I came up with this code from a different article and changed it an extension method.
public static void ToTransparent(this System.Windows.Forms.Button Button,
System.Drawing.Color TransparentColor)
{
Bitmap bmp = ((Bitmap)Button.Image);
bmp.MakeTransparent(TransparentColor);
int x = (Button.Width - bmp.Width) / 2;
int y = (Button.Height - bmp.Height) / 2;
Graphics gr = Button.CreateGraphics();
gr.DrawImage(bmp, x, y);
}
And the call like:
buttonUpdate.ToTransparent(Color.Magenta);