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]

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]

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]

ofiras wrote:
> 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.

--
Göran Andersson
_____
http://www.guffa.com

[Peter Bromberg[C# MVP]]

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

"ofiras" <ofi...@gmail.com> wrote in message
news:e5b1bd81-9115-4849...@c58g2000hsc.googlegroups.com...

[ofiras]

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?

[Peter Duniho]

On Tue, 05 Aug 2008 01:24:51 -0700, Pavel Minaev <int...@gmail.com> wrote:

> [...]

>> 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, yes and no. Assuming an untransformed, pixel-units Graphics
instance, Graphics.FillRectangle() would work fine. And assuming a
_transformed_ Graphics instance, you shouldn't be worrying about reliably
drawing exactly 1 pixel anyway (and under such a transformation, a
single-pixel bitmap is going to be transformed as well).

I don't see any real benefit to creating a whole Bitmap instance just to
draw a pixel (and that's even if you do cache it).

That said, I have a suspicion, based on the use of Graphics.FromHwnd(),
that the OP has some more fundamental problems with respect to maintaining
paint state.

Pete

[Pavel Minaev]

On Aug 5, 8:49 pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com>
wrote:

> 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?

[Peter Duniho]

Do you have anti-aliasing turned on? If so, then that's a variation of a
"transformed" graphics output and carries the same aspect that one should
not care about getting exactly a single pixel. If you are drawing to a
non-anti-aliased output, you should get one pixel.

Pete