I've not fully understand the basics of Bit blit bitmaps.
I'm using the WriteableBitmapEx framework (WPF). My bitmap represents a map and what I wanna achieve is to copy a (moving) symbol into that map.
For actual copying, I use the function Blit:
_bitmap.Blit(myObject.Value.Location.ToWindowsPoint(), symbol, rect, Colors.Cyan,
WriteableBitmapExtensions.BlendMode.Additive);
where symbol is a png image(transparent background).
This works in prinicpal but I do not understand how the color (Colors.Cyan) is applied by the blend mode. I've tried out all available blend modes but I've not succeeded in getting Cyan as the color of the symbol or I got the color but then the transparent background was also copied to the source bitmap (black background).
Is 'Bliting' the wrong approach for my use case?
Thanks.
A much easier approach is to use images (corresponding WPF ui element) and layer it above the bitmap. This has also the advantage that you can move the image without redrawing the bitmap at all.
Related
I managed to show a gif almost perfectly with the disposal methods and everything, but I have a big trouble with the transparent color.
I saw other apps that draw a previous bmp on the next successfully.
I don't know how to do it.
I think I need to use transparentblt but I don't know how to set the transparent color. I work with 32-bit bitmaps, the transparent color of each frame I take correctly from the gif frame palette,
but I don't know if I should and how to set the alpha channel of the color.
In the beginning I tried to replace each transparent color with 0x80000000 and use the bitmap with both bitblt/transparentblt,
but no luck.
Maybe my problem is only the alpha channel of the transparent color? What value should it get?
I actually think my problem is only drawing bitmap on another with transparent color.
Since I have the transparent color I'll think I can do it myself
even if I'll have to transfer the bytes byte by byte.
I still don't know whether TransparentBlt API can do it though.
Does anyone know how to apply brightness and contrast control to an Image in silverlight 5? Maybe using UIElement.Effect? I don't need to modify/save the image, just change how it is displayed.
Use a WriteableBitmap as source for your image and then apply a brightness/contrast formula on every pixel of the WriteableBitmap.
You need to call Invalidate() on your bitmap instance after you have changed the pixels.
I ended up using a Custom Pixel Shader. Shazzam has a contrast adjust custom pixel shader in it's pre-installed samples. The beauty of this is that it works in both WPF and silverlight.
The System.Drawing.Graphics class has a property CompositionMode with two options: SourceOver (which, based on the alpha component, blends whatever is drawn with the background already existing) or SourceCopy which simply overwrites the background with whatever is being drawn.
Does something similar exist in WPF?
In WPF when i draw a PolyLine for example on top of another the new PolyLine always alphablends with the background. I think that is independent of the container being used. I am using a Canvas but could not find a blend mode property anywhere. What I want to do is what the SourceCopy compositionmode mentioned above does. I.e. the new PolyLine should simply overwrite whatever is already on the Canvas.
Is there a simple way to do that, short of using pixel shaders (which - as far as I understand - wouldn't work anyways because I don't have access to the Canvas backbuffer).
I am not stuck with a Canvas and would be happy to use any container that supports overwrite mode.
I currently have a solution based on a WriteableBitmap for which I obtain a System.Drawing.Graphics context and then manipulate the CompositionMode. It works but since my window is fullscreen that solution has serious performance impacts.
Clarification and example:
The WPF window is fully transparent and so is the Canvas (back ground color(0,0,0,0)). Now I draw a PolyLine with a Color.FromArgb(128,128,0,0). I now have a semi-transparent red polyline. Next I draw the same PolyLine with Color.FromArgb(0,0,0,0). The result is the same as before because of the alpha blending taking place. What I want, however, is that the red polyline is erased with the second polyline (which is exactly what the SourceCopy mode in the Graphics class does.
I think all you need to do is make sure that the brushes used to fill/stroke the PolyLine have fully opaque alpha values (i.e. 255). Then the background shouldn't be blended into it.
You could apply a Clipping Mask, this way you can provide the path to clip over the elements that are below it, but it might be tough to maintain after a lot elements are required to be clipped...
What i'm trying to do is making a "light projector" with visible ray(like with fog) also called volumetric light;
and which project a image (bitmap) ;
Because i would like to keep this project connected with a wpf application ( to get brush, position, rotation from data), i've choose to use WPF 3D
But it seem that WPF can't handle light projection or render ray.
So to do that, i have extruded each pixel of my source bitmap into a polygon colored by a solidColorBrush of the pixel color.
and keep the pixel order with (x,y) position.
For performance issue, i've set all the bitmaps to 32x32 px ( 1024 polygon for only one light !!)
But the result is too pixelated as you can see on the picture.
Moreover, it probably take much memory for nothing ...
my question is, how can i make it smooth or even rethink the extrusion system to optimize performance ...
Is any other tehnology that can be integrated into a wpf application and do that better or easier ?
Thanks, and sorry my English is pretty bad ...
alt text http://www.visualdmx.fr/pic_example.png
I want to put an image on a button, but I want part of the image to be transparent. How do I do this?
Try the Image.OpacityMask property. You can give it a brush that specifies the region you want to be transparent.
EDIT: From MSDN:
There is no direct support for
color-keying a bitmap in WPF.
However, it is fairly easy to
implement on your own. Dwayne has
implemented a ColorKeyBitmap on his
blog:
http://blogs.msdn.com/dwayneneed/archive/2008/06/20/implementing-a-custom-bitmapsource.aspx
I believe it links to the code on
Codeplex as well. You could also
accomplish this simply by reading your
bitmap into system memory, iterating
through all the pixels and setting
their values yourself, and
constructing a new bitmap out of that
array.
Use a paint program (I use Paint.Net) to change the area you want transparent to an alha=0 color. Then save the image (mine was JPG) as a PNG. Seemed to work fine for me in the WPF Image control.