How Can I Paint a Pixel?

[ofiras]

Hi,
I made a "Paint" program, but I couldn't find a method to paint 1
pixel using graphic state ("Graphics g =
Graphics.FromHwnd(this.Handle);")
How can I paint 1 pixel?
I guess I can make a Bitmap, change one pixel color and show it, but
I'm sure there is another way of doing it.
Please help,
Ofir.

 

[Pavel Minaev]

Hi,
I made a "Paint" program, but I couldn't find a method to paint 1
pixel using graphic state ("Graphics g =
Graphics.FromHwnd(this.Handle);")
How can I paint 1 pixel?
I guess I can make a Bitmap, change one pixel color and show it, but
I'm sure there is another way of doing it.

There isn't. GDI+ is a resolution-independent drawing framework, and
the underlying device may not even be a raster device, in theory (GDI+
plotter, anyone?). So painting a single-pixel bitmap is about the only
workaround (there's no way to draw a 1-pixel-long line or rectangle
reliably).

Well, or you can use plain GDI via P/Invoke - that has SetPixel().

 

[ofiras]

There isn't. GDI+ is a resolution-independent drawing framework, and
the underlying device may not even be a raster device, in theory (GDI+
plotter, anyone?). So painting a single-pixel bitmap is about the only
workaround (there's no way to draw a 1-pixel-long line or rectangle
reliably).

Well, or you can use plain GDI via P/Invoke - that has SetPixel().

Thanks... I'll use Bitmap to paint pixel...
One more question - How can I save graphics that the user has drawn to
Bitmap?
Or how can I draw line/circle in Bitmap (so every time the user wii
draw a line or a circle I can do it in the Bitmap too)?
Please help,
Ofir.

 

[Göran Andersson]

How can I save graphics that the user has drawn to
Bitmap?

Well, how do you keep the graphics so that you can repaint it on the screen?

Or how can I draw line/circle in Bitmap (so every time the user wii
draw a line or a circle I can do it in the Bitmap too)?

You use the Graphics.FromImage method to create a Graphics object that
you can use to draw on the Bitmap.

 

[Peter Bromberg[C# MVP]]

The System.Drawing.Bitmap class has a SetPixel and GetPixel method.

 

[ofiras]

Well, how do you keep the graphics so that you can repaint it on the screen?


You use the Graphics.FromImage method to create a Graphics object that
you can use to draw on the Bitmap.

Thanks, it helped a lot.
Another question - in bitmap, how can I find the nearest pixel (pixel
1) to a specific pixel (pixel 2) that has different color from pixel
2? Or how can I find a pixel in a specific distance from pixel 2 (like
a circle that pixel 2 is his center, and I'm looking for a pixel that
has different color that pixel 2)?
(I'm trying to do a voronoi diagram maker, so I need to search for the
nearest colored pixel in my bitmap for every pixel that is not colored
(white))

And one more question - how can I load picture and change its width
and height?

 

[Pavel Minaev]

Well, yes and no.  Assuming an untransformed, pixel-units Graphics  
instance, Graphics.FillRectangle() would work fine.

It didn't when I tried it. If you specify the size of the rectangle to
draw as 1x1, then it actually paints a 2x2 pixel block. If you specify
size as 0x0, it doesn't paint it at all. Or do you propose to feed it
fractional values in hope that it will get the rounding correctly?