How do I draw a circular gradient like this in vb.net?
Check out this great page. The code in the article is in C#. Here is a VB.NET port of the code you're interested in and updated for a rectangular fill (based on the article's triangle fill sample):
Dim pgb As New PathGradientBrush(New Point() { _
New Point(0, 0), _
New Point(0, Me.ClientRectangle.Height), _
New Point(Me.ClientRectangle.Width, Me.ClientRectangle.Height), _
New Point(Me.ClientRectangle.Width, 0)})
pgb.SurroundColors = New Color() {Color.Red}
pgb.CenterColor = Color.Gray
e.Graphics.FillRectangle(pgb, Me.ClientRectangle)
pgb.Dispose()
Here's another possible solution:
Dim pth As New GraphicsPath()
pth.AddEllipse(Me.ClientRectangle)
Dim pgb As New PathGradientBrush(pth)
pgb.SurroundColors = New Color() {Color.Red}
pgb.CenterColor = Color.Gray
e.Graphics.FillRectangle(pgb, Me.ClientRectangle)
Note that this last code snippet will draw a circle bounded inside of a rectangle. If you want the circular gradient to fill the entire rectangle you'll have to calculate a larger elliptic path with a larger rectangle.
Related
Is there some way to copy a GraphicsPath and the enclosed figure into a new picture?
I have the rectangle, the points of the GraphicsPath available. The path is definitely in the rectangle.
I already googled but the result is poor. So far, I can only copy a certain area (rectangle) into a new picture, see source code.
Using Extracted As Bitmap = New Bitmap(rect.Width, rect.Height, Imaging.PixelFormat.Format32bppArgb)
Using Grp As Graphics = Graphics.FromImage(Extracted)
Grp.DrawImage(Picture1, 0, 0, rect, GraphicsUnit.Pixel)
End Using
If System.IO.Directory.Exists("C:\Users\xy\Desktop") Then
Extracted.Save("C:\Users\xy\Desktop\1.png", Imaging.ImageFormat.Png)
End If
End Using
I have found something here:
This is the solution translated into VB.Net and with Option Strict On and Option Infer Off.
Using bmpSource As Bitmap = New Bitmap(Form1.Pfad_Bild)
Dim rectCutout As RectangleF = gp.GetBounds()
Using m As Matrix = New Matrix()
m.Translate(-rectCutout.Left, -rectCutout.Top)
gp.Transform(m)
End Using
Using bmpCutout As Bitmap = New Bitmap(CInt(rectCutout.Width), CInt(rectCutout.Height))
Using graphicsCutout As Graphics = Graphics.FromImage(bmpCutout)
graphicsCutout.Clip = New Region(gp)
graphicsCutout.DrawImage(bmpSource, CInt(-rectCutout.Left), CInt(-rectCutout.Top))
If System.IO.Directory.Exists("C:\Users\xy\Desktop") Then
bmpCutout.Save("C:\Users\xy\Desktop\1.png", Imaging.ImageFormat.Png)
End If
End Using
End Using
End Using
i am working in a project where i have to convert a bitmap image from a screenshot to a mat format directly in order to use it with engu opencv. it only works when i save the image and call it with New Mat() funtion.
Public Function ScreenShot() As Bitmap
Dim screenSize As Size = New Size(My.Computer.Screen.Bounds.Width,
My.Computer.Screen.Bounds.Height)
Dim screenGrab As New Bitmap(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
Dim g As Graphics = Graphics.FromImage(screenGrab)
g.CopyFromScreen(New Point(0, 0), New Point(0, 0), screenSize)
screenGrab.Save("C:\Users\Desktop\test.png")
imgOriginal = New Mat("C:\Users\Desktop\test.png")
screengrab is the bitmap but how can i use it directly as a mat format without saving it?.
i think this saving operation could damage the hard drive because it is saving and reading this every second.
In VB.NET, I need to create an Image based on a Graphics object I have. However, there is no method such as Image.fromGraphics() etc. What should I do then?
Try something like this MSDN article states. Essentialy create a Graphics Object from a Bitmap. Then use Graphic methods to do what you need to to the Image and then you can use the Image how you need to. As #Damien_The_Unbeliever stated your Graphics Object is created to enable drawing on another object, it does not have an Image to copy, the object it was created on does.
From above article:
Dim flag As New Bitmap(200, 100)
Dim flagGraphics As Graphics = Graphics.FromImage(flag)
Dim red As Integer = 0
Dim white As Integer = 11
While white <= 100
flagGraphics.FillRectangle(Brushes.Red, 0, red, 200, 10)
flagGraphics.FillRectangle(Brushes.White, 0, white, 200, 10)
red += 20
white += 20
End While
pictureBox1.Image = flag
Have a look at the Graphics.DrawImage method and its overloads.
Here's a snippet from one of the examples that draws an image onto the screen, using a Graphics object from Winform's Paint event:
Private Sub DrawImageRect(ByVal e As PaintEventArgs)
' Create image.
Dim newImage As Image = Image.FromFile("SampImag.jpg")
' Create rectangle for displaying image.
Dim destRect As New Rectangle(100, 100, 450, 150)
' Draw image to screen.
e.Graphics.DrawImage(newImage, destRect)
End Sub
I'm drawing text in VB.net by using:
gfx.DrawString(_bText, New Font("Tahoma", 5), Brushes.Black, New Point(25, 5))
where gfx is a graphics object using my control. The x point is correct but I need the y to be the center of the current contol (vertically). Is there an easy way to do this?
You need to look at the Graphics.MeasureString method
Using this you can find the Height of your text in the context you give it. You then need to find the Y value to start drawing your text using something like this:
(ControlHeight/2) - (TextHeight/2)
Use the DrawString overload that takes a StringFormat argument. Set its Alignment property to Center.
TextRenderer has a VerticalCenter flag:
Dim r As New Rectangle(25, 0, myControl.ClientSize.Width - 25, _
myControl.ClientSize.Height)
Using myFont As New Font("Tahoma", 5)
TextRenderer.DrawText(gfx, _bText, myFont, r, _
Color.Black, Color.Empty, _
TextFormatFlags.VerticalCenter)
End Using
Okay, I've learned a bit more and have rephrased my question. I've got a need to flip or invert text 180 degrees (so it appears upside-down) on a RDLC report. I have some custom VB code that takes the text, converts it to a bitmap, then flips the rotates the canvas 180 degrees. The effect of this makes the text look a bit.. dithered... or fuzzy. It's not a sharp font anymore. The problem I'm experiencing is I'm using a special TTF Barcode font that creates something a scanner can read. When I flip the barcode font, the fuzziness isn't good since the barcode lines are so close together and the scanner cannot read it. Here's the code:
Function LoadImage(ByVal sImageText as String, iRotationAngle as Integer, ByVal sFontName as String, iFontSize as Integer)
Dim bmpImage As New Drawing.Bitmap(1, 1)
Dim iWidth As Integer = 0
Dim iHeight As Integer = 0
'// Create the Font object for the image text drawing.
Dim MyFont As New Drawing.Font(sFontName, iFontSize) ', System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point)
'// Create a graphics object to measure the text's width and height.
Dim MyGraphics As Drawing.Graphics = Drawing.Graphics.FromImage(bmpImage)
'// This is where the bitmap size is determined.
iWidth = MyGraphics.MeasureString(sImageText, MyFont).Width
iHeight = MyGraphics.MeasureString(sImageText, MyFont).Height
'// Create the bmpImage again with the correct size for the text and font.
bmpImage = New Drawing.Bitmap(bmpImage, New Drawing.Size(iWidth, iHeight))
'// Add the colors to the new bitmap.
MyGraphics = Drawing.Graphics.FromImage(bmpImage)
MyGraphics.Clear(Drawing.Color.White)
MyGraphics.TextRenderingHint = Drawing.Text.TextRenderingHint.ClearTypeGridFit
MyGraphics.TranslateTransform(iWidth,iHeight)
MyGraphics.RotateTransform(iRotationAngle)
MyGraphics.DrawString(sImageText, MyFont, New Drawing.SolidBrush(Drawing.Color.Black), 0, 0)
MyGraphics.Flush()
Dim stream As IO.MemoryStream = New IO.MemoryStream
Dim bitmapBytes As Byte()
'Create bitmap
bmpImage.Save(stream, System.Drawing.Imaging.ImageFormat.Bmp)
bitmapBytes = stream.ToArray
stream.Close()
bmpImage.Dispose()
Return bitmapBytes
End Function
I really don't know why there's not a built-in way to just flip text. It'll let me reverse it left-to-right. Ridiculous.
Thanks