Develop Reference

wpf create transparent writeablebitmap

When I create one like this:
WriteableBitmap wb = new WriteableBitmap(1200, 1600, 90, 90, PixelFormats.Bgr24, null);
Its filled with black when I want it to be transparent. I tried Clear(from WriteableBitmapEx library) but I get a Attempted to read or write protected memory. This is often an indication that other memory is corrupt."} System.Exception {System.AccessViolationException}
wb.Clear(Colors.Transparent);
Any ideas how I could accomplish this?
Edit:
List<FormattedText> text = new List<FormattedText>();
WriteableBitmap wb = new WriteableBitmap(1200, 1600, 96, 96, PixelFormats.Bgr32, null);
wb.Clear(Colors.Transparent);
TransformedBitmap tb = new TransformedBitmap(wb, new RotateTransform(0));
DrawingVisual drawingVisual = new DrawingVisual();
DrawingContext drawingContext = drawingVisual.RenderOpen();
drawingContext.DrawImage(tb, new Rect(0, 0, tb.PixelWidth, tb.PixelHeight));
for (int i = 0; i < text.Count; i++)
{
drawingContext.DrawText(text[i], points[i]);
drawingContext.DrawEllipse(null, new Pen(new SolidColorBrush(Colors.Aqua), 3), points[i], 10, 10);
}
drawingContext.Close();
System.Windows.Media.Imaging.RenderTargetBitmap bmp = new System.Windows.Media.Imaging.RenderTargetBitmap(tb.PixelWidth, tb.PixelHeight, 96, 96, PixelFormats.Pbgra32);
bmp.Render(drawingVisual);
Image = bmp;

Create the WriteableBitmap with a PixelFormat that has an alpha channel and thus allows for transparency, e.g. PixelFormats.Bgra32:
var wb = new WriteableBitmap(1200, 1600, 96, 96, PixelFormats.Bgra32, null);
Now you have four bytes per pixel, one for blue, one for green, one for red, and one for the alpha value.
Note also that you would usually use a value of 96 for the DPI parameters.

How to show dropshadow on drawingcontext tools

Actually i am using drawingContext.DrawRectangle method for drawing rectangle on canvas..
i want to add shadow effect on rectangle..
drawingContext.DrawRectangle(new SolidColorBrush(graphicsObjectFillColor),
new Pen(new SolidColorBrush(ObjectColor), ActualLineWidth),
Rectangle);
or i am using this to add drop shadow..
DropShadowEffect effect = new DropShadowEffect();
effect = new DropShadowEffect { Color = Colors.Black, Direction = -45, Opacity = 0.5, ShadowDepth = 4};
this.Effect = effect;
the shadow is showing but add the time of draw all tool on image tha shodow is not shawing
i am using
DrawingVisual vs = new DrawingVisual();
DrawingContext dc = vs.RenderOpen();
// Draw image
dc.DrawImage(image.Source, rect);
double scale = width / image.Source.Width;
// Keep old existing actual scale and set new actual scale.
double oldActualScale = drawingCanvas.ActualScale;
drawingCanvas.ActualScale = oldActualScale;
// Remove clip in the canvas - we set our own clip.
drawingCanvas.RemoveClip();
// Prepare drawing context to draw graphics
rect = new Rect(left, top, width, height);
dc.PushClip(new RectangleGeometry(rect));
double horizontalScale = Math.Abs((positionDrawingCanvas.X) - (positionImage.X));
double verticalScale = Math.Abs((positionDrawingCanvas.Y) - (positionImage.Y));
double difX = 0.0;
double difY = 0.0;
//if (horizontalScale != 0 && verticalScale != 0)
//{
// //horizontalScale = Math.Abs((positionDrawingCanvas.X + Math.Abs((positionImage.X / sliderScale.Value - positionImage.X))) - (positionImage.X));
// //verticalScale = Math.Abs((positionDrawingCanvas.Y + Math.Abs((positionImage.Y / sliderScale.Value - positionImage.Y))) - (positionImage.Y));
// difX = (positionImage.X - positionImage.X / sliderScale.Value);
// difY = (positionImage.Y - positionImage.Y / sliderScale.Value);
//}
dc.PushTransform(new TranslateTransform(difX + left - horizontalScale, difY+top - verticalScale));
dc.PushTransform(new ScaleTransform(1, 1));
// Ask canvas to draw overlays
drawingCanvas.Draw(dc);
// Restore old actual scale.
drawingCanvas.ActualScale = oldActualScale;
// Restore clip
drawingCanvas.RefreshClip();
dc.Pop();
dc.Pop();
dc.Pop();
dc.Close();
width = (Utilityhelper.GetDIPIndependentHorizontal(rect.Width));
height = (Utilityhelper.GetDIPIndependentVertical(rect.Height));
bmp = new RenderTargetBitmap((int)width, (int)(height), Utilityhelper.graphics.DpiX, Utilityhelper.graphics.DpiY, PixelFormats.Default);
//bmp = new RenderTargetBitmap((int)(scale * (rect.Width)), (int)(scale * (rect.Height)), scale * 96, scale * 96, PixelFormats.Default);
bmp.Render(vs);
sliderScale.Value = oldScale;
//imageBackground.Stretch = Stretch.Uniform;
//drawingCanvas.Width = (Utilityhelper.GetDIPDependentHorizontal(drawingCanvas.Width));
//drawingCanvas.Height = (Utilityhelper.GetDIPDependentVertical(drawingCanvas.Height));
return bmp;

You have to just change your render method
RenderTargetBitmap bmp = new RenderTargetBitmap((int)width, (int)(height), DpiX, DpiY, PixelFormats.Default);
BitmapSource source = null;
if (bmp != null)
{
bmp.Render(image);
bmp.Render(drawingCanvas);
source = bmp;
}

Here is how you get image (bitmap) from visual in wpf:
// render content into image
var render = new RenderTargetBitmap((int)ContentPresenter.RenderSize.Width, (int)ContentPresenter.RenderSize.Height, 96, 96, PixelFormats.Default);
render.Render(ContentPresenter);
var encoder = new PngBitmapEncoder();
encoder.Frames.Add(BitmapFrame.Create(render));
using (var stream = new MemoryStream())
{
// create bitmap image
encoder.Save(stream);
var bitmap = new BitmapImage();
bitmap.BeginInit();
bitmap.StreamSource = stream;
bitmap.CacheOption = BitmapCacheOption.OnLoad;
bitmap.EndInit();
bitmap.Freeze();
// use BitmapImage
...
}
ContentPresenter is some visual.

re-sizing image in c# doesn't work

I am trying to resize image to width=100 height=100
public ActionResult RegisterUser(userAuthModel user, HttpPostedFileBase userimage)
{
if (userimage.ContentLength > 0 && userimage != null)
{
string fname = userimage.FileName;
var path = Server.MapPath("~/Images/User_DP/" + userimage.FileName);
var image_100 = new System.Drawing.Bitmap(userimage, new Size(100, 100));
userimage.SaveAs(path);
}
.
.
.
.
.
}
Here I am using bitmap approach to resize imgae to some specific width and height.
But this shows me error in line-
var image_100 = new System.Drawing.Bitmap(userimage, new Size(100, 100));
of invalid arguments. How Do Ii resize image with using bitmap?

The System.Drawing.Bitmap class asks for two parameters in the constructor your are using:
System.Drawing.Image
System.Drawing.Size
In your code, you are passing the size correctly, but not the image. HttpPostedFileBase does not extend the Image class.
You will need to change that part of your code. If you are using the HttpPostedFileBase as a stream, then keep in mind that System.Drawing.Bitmap has no constructor asking for a Stream and a Size.
References:
System.Drawing.Image
System.Web.HttpPostedFileBase

you have to use mentioned method it may help you
private static BitmapFrame CreateResizedImage(ImageSource source, int width, int height, int margin)
{
var rect = new Rect(margin, margin, width - margin * 2, height - margin * 2);
var group = new DrawingGroup();
RenderOptions.SetBitmapScalingMode(group, BitmapScalingMode.HighQuality);
group.Children.Add(new ImageDrawing(source, rect));
var drawingVisual = new DrawingVisual();
using (var drawingContext = drawingVisual.RenderOpen())
drawingContext.DrawDrawing(group);
var resizedImage = new RenderTargetBitmap(
width, height, // Resized dimensions
96, 96, // Default DPI values
PixelFormats.Default); // Default pixel format
resizedImage.Render(drawingVisual);
return BitmapFrame.Create(resizedImage);
}

Rendering a UserControl in code rather than XAML

I want to use RenderTargetBitmap to render a UserControl to a bitmap without having to write the XAML for it. When I do this I get a blank image, am I missing a crucial step?
ValTool.Controls.VideoFisheyeOverlayControl vfoc = new Controls.VideoFisheyeOverlayControl();
vfoc.Width = (int)this.VideoContainer.ActualWidth;
vfoc.Height = (int)this.VideoContainer.ActualHeight;
vfoc.FieldsOfView=this.FieldsOfView;
vfoc.CountLines = this.CountLines;
vfoc.UpdateLayout();
vfoc.InvalidateVisual();
RenderTargetBitmap visual = new RenderTargetBitmap((int)this.VideoContainer.ActualWidth, (int)this.VideoContainer.ActualHeight, 96, 96, PixelFormats.Pbgra32);
visual.Render(vfoc);
var finalImage = BitmapFrame.Create(visual);
// Encoding the RenderBitmapTarget as a PNG file.
PngBitmapEncoder png = new PngBitmapEncoder();
png.Frames.Add(BitmapFrame.Create(finalImage));
using (Stream stm = File.Create(#"new.png"))
{
png.Save(stm);
}

Instead of UpdateLayout you have to call Measure and Arrange to get the layout done:
var width = VideoContainer.ActualWidth;
var height = VideoContainer.ActualHeight;
vfoc.Measure(new Size(width, height));
vfoc.Arrange(new Rect(0, 0, width, height));
vfoc.InvalidateVisual();

RenderTargetBitmap problem

I am trying to add the image of a usercontrol to viewbox.
I am creating the usercontrol dynamically. I am using the code below.
private static RenderTargetBitmap CaptureScreen(Visual target, double dpiX, double dpiY)
{
if (target == null)
{
return null;
}
Rect bounds = VisualTreeHelper.GetDescendantBounds(target);
//RenderTargetBitmap rtb = new RenderTargetBitmap((int)(bounds.Width * dpiX / 96.0),
// (int)(bounds.Height * dpiY / 96.0),
// dpiX,
// dpiY,
// PixelFormats.Pbgra32);
RenderTargetBitmap rtb = new RenderTargetBitmap(596,596,dpiX,
dpiY,
PixelFormats.Pbgra32);
DrawingVisual dv = new DrawingVisual();
using (DrawingContext ctx = dv.RenderOpen())
{
VisualBrush vb = new VisualBrush(target);
ctx.DrawRectangle(vb, null, new Rect(new Point(), bounds.Size));
}
rtb.Render(dv);
return rtb;
}
I am creating the user control dynamically and passing this to capture screen method.
UserControls.UserControl1 uc1 = new UserControls.UserControl1();
visualList.Add(uc1);
for(int i = 0;i<=6;i++)
{
Image img = new Image();
img.Source = CaptureScreen(visualList[i], 96, 96);
img.Margin = new Thickness { Top = 2 };
usingWorkaround.Children.Add(img);
}
the VisualTreeHelper.GetDescendantBounds(target) is returning empty bounds. Thats why the image of the screen can not be created. Is there any other method to capture screen of dynamically created user control?

you can call Measure and Arrange As follows
private void ForceUpdate(FrameworkElement element, double width, double height)
{
Size size = new Size(width, height);
element.Measure(size);
element.Arrange(new Rect(0, 0, width, height));
element.UpdateLayout();
}

At the time when you try to create the image the controls don't yet exist in the visual tree and the size has not been calculated.
You will need to call Measure and Arrange on your visual first.