On Nov 3, 11:59 pm, Loren Pechtel <lorenpech... at (no spam) hotmail.invalid.com
wrote:
I'm having trouble with what seems to be a simple task:

I'm trying to draw some vector images on a field of tiles.  The tiles
are always of integer sizes and can zoom over any reasonable range of
values.

The images themselves are vector images but they don't simply scale
up, as the tile gets bigger more detail is added.  (Yeah, I know I'll
have to handle printing a bit differently.)

The problem I'm having is with images composed entirely of vertical
and horizontal lines, black on a gray field.

The horizontal lines are fine, I get exactly what I want.  Vertical
lines aren't working too well, though.  A lone vertical line is good
enough--two pixels of dark gray instead of one of black but it looks
close enough I didn't even realize it was wrong until I got digging
into the case that's awful:

I have some stripes, some are black/background/background and others
are black/background.

With antialiasing on the ones with the black every three look fuzzy
and the closer ones just look like a blurry blob.

With it turned off I'm getting a very clear image, albeit very wrong:
The three-step one produces dark gray/dark gray/background and the
two-step one simply produces a box of dark gray.

Everything is being drawn on a bitmap that is then put in a
picturebox.  The picturebox is in a panel that fills the form other
than a few controls on the right for manipulating the view.

The behavior would make sense if somehow I was drawing between pixels
on the y axis but all the DrawLines are being fed integer coordinates.

My psychic powers must be off today, everything is blurry. Can't see
the code, the size of the bitmap, the size of the picturebox,
properties
of the picturebox, the comments in the code, in fact, even the code!

On a guess, try making the window 1 pixel wider, see if anything
changes.

I agree it sounds exactly like fractional coordinates. How do you
draw on fractional coordinates with integer variables, though? [...]

I'm having trouble with what seems to be a simple task:

I'm trying to draw some vector images on a field of tiles. The tiles
are always of integer sizes and can zoom over any reasonable range of
values.

The images themselves are vector images but they don't simply scale
up, as the tile gets bigger more detail is added. (Yeah, I know I'll
have to handle printing a bit differently.)

The problem I'm having is with images composed entirely of vertical
and horizontal lines, black on a gray field.

The horizontal lines are fine, I get exactly what I want. Vertical
lines aren't working too well, though. A lone vertical line is good
enough--two pixels of dark gray instead of one of black but it looks
close enough I didn't even realize it was wrong until I got digging
into the case that's awful:

I have some stripes, some are black/background/background and others
are black/background.

With antialiasing on the ones with the black every three look fuzzy
and the closer ones just look like a blurry blob.

With it turned off I'm getting a very clear image, albeit very wrong:
The three-step one produces dark gray/dark gray/background and the
two-step one simply produces a box of dark gray.

Everything is being drawn on a bitmap that is then put in a
picturebox. The picturebox is in a panel that fills the form other
than a few controls on the right for manipulating the view.

The behavior would make sense if somehow I was drawing between pixels
on the y axis but all the DrawLines are being fed integer coordinates.

I have to ask: are you absolutely positive you're actually getting
different-colored pixels, or does it just LOOK that way. In other words,
have you saved your bitmap to disk and then loaded it into a graphics
application and increased the zoom so that you can see the individual
pixels?

Loren Pechtel wrote:
I agree it sounds exactly like fractional coordinates. How do you
draw on fractional coordinates with integer variables, though? [...]

By drawing in an environment where coordinates given as integers are
scaling somehow.

I posted a code example that shows that in general, the problem you
describe does not occur. Either your own code does something different,
or you are simply not observing the results correctly (i.e. you think
there's a problem when there's not).

In the latter case, obviously there's nothing to fix. In the former
case, until you post a concise-but-complete code example that reliably
demonstrates the issue, there's no way to tell you how to fix your code.

"Loren Pechtel" <lorenpechtel at (no spam) hotmail.invalid.com> wrote in message
news:%23edaYuQXKHA.1280 at (no spam) TK2MSFTNGP04.phx.gbl...

I'm having trouble with what seems to be a simple task:

I'm trying to draw some vector images on a field of tiles. The tiles
are always of integer sizes and can zoom over any reasonable range of
values.

The images themselves are vector images but they don't simply scale
up, as the tile gets bigger more detail is added. (Yeah, I know I'll
have to handle printing a bit differently.)

The problem I'm having is with images composed entirely of vertical
and horizontal lines, black on a gray field.

The horizontal lines are fine, I get exactly what I want. Vertical
lines aren't working too well, though. A lone vertical line is good
enough--two pixels of dark gray instead of one of black but it looks
close enough I didn't even realize it was wrong until I got digging
into the case that's awful:

I have some stripes, some are black/background/background and others
are black/background.

With antialiasing on the ones with the black every three look fuzzy
and the closer ones just look like a blurry blob.

With it turned off I'm getting a very clear image, albeit very wrong:
The three-step one produces dark gray/dark gray/background and the
two-step one simply produces a box of dark gray.

Everything is being drawn on a bitmap that is then put in a
picturebox. The picturebox is in a panel that fills the form other
than a few controls on the right for manipulating the view.

The behavior would make sense if somehow I was drawing between pixels
on the y axis but all the DrawLines are being fed integer coordinates.

I have to ask: are you absolutely positive you're actually getting
different-colored pixels, or does it just LOOK that way. In other words,
have you saved your bitmap to disk and then loaded it into a graphics
application and increased the zoom so that you can see the individual
pixels?

Jeff Johnson wrote:
I have to ask: are you absolutely positive you're actually getting
different-colored pixels, or does it just LOOK that way. In other words,
have you saved your bitmap to disk and then loaded it into a graphics
application and increased the zoom so that you can see the individual
pixels?

To elaborate on this point: the code example I posted last evening is
specifically designed to illustrate this point. It provides for scaling
the image during presentation, as well as inspecting RGB values for any
specific pixel.

With the example, you can see that scaling the image by (for example)
200%, you get the aliasing behavior described by the OP, but the pixel
values are still exactly as he wants (i.e. 0,0,0 RGB where a black line
is drawn, 128,128,128 on the gray background where it wasn't).

On Wed, 04 Nov 2009 12:30:56 -0800, Peter Duniho
no.peted.spam at (no spam) no.nwlink.spam.com> wrote:

Loren Pechtel wrote:
I agree it sounds exactly like fractional coordinates. How do you
draw on fractional coordinates with integer variables, though? [...]
By drawing in an environment where coordinates given as integers are
scaling somehow.

I posted a code example that shows that in general, the problem you
describe does not occur. Either your own code does something different,
or you are simply not observing the results correctly (i.e. you think
there's a problem when there's not).

In the latter case, obviously there's nothing to fix. In the former
case, until you post a concise-but-complete code example that reliably
demonstrates the issue, there's no way to tell you how to fix your code.

I managed to reproduce it very easily:

A form containing a panel that contains a picture box. Drawing:

Bitmap Image = new Bitmap(Box.ClientSize.Width
,Box.ClientSize.Height);
Pen Ink = new Pen(Color.Black, -1);
using (Graphics Paper = Graphics.FromImage(Image))
{
Paper.Clear(Color.LightGray);
for (int x = 2; x < Image.Width / 2; x += 2)
Paper.DrawLine(Ink, x, 0, x, Image.Height - 1);
for (int y = 2; y < Image.Height; y += 2)
Paper.DrawLine(Ink, Image.Width / 2, y, Image.Width -
1, y);
}
Box.Image = Image;

Obviously the panel in this case is useless but I simply copied the
layout from the main code--in the main code there are some controls
off to the side and I use the panel to make the picture box take up
the whole form.

This code *SHOULD* draw one half of the screen with vertical lines and
one half with horizontal. I'm getting a gray mass on the left and the
expected behavior on the right.

Loren Pechtel wrote:
On Wed, 04 Nov 2009 12:30:56 -0800, Peter Duniho
no.peted.spam at (no spam) no.nwlink.spam.com> wrote:

Loren Pechtel wrote:
I agree it sounds exactly like fractional coordinates. How do you
draw on fractional coordinates with integer variables, though? [...]
By drawing in an environment where coordinates given as integers are
scaling somehow.

I posted a code example that shows that in general, the problem you
describe does not occur. Either your own code does something different,
or you are simply not observing the results correctly (i.e. you think
there's a problem when there's not).

In the latter case, obviously there's nothing to fix. In the former
case, until you post a concise-but-complete code example that reliably
demonstrates the issue, there's no way to tell you how to fix your code.

I managed to reproduce it very easily:

A form containing a panel that contains a picture box. Drawing:

Bitmap Image = new Bitmap(Box.ClientSize.Width
,Box.ClientSize.Height);
Pen Ink = new Pen(Color.Black, -1);
using (Graphics Paper = Graphics.FromImage(Image))
{
Paper.Clear(Color.LightGray);
for (int x = 2; x < Image.Width / 2; x += 2)
Paper.DrawLine(Ink, x, 0, x, Image.Height - 1);
for (int y = 2; y < Image.Height; y += 2)
Paper.DrawLine(Ink, Image.Width / 2, y, Image.Width -
1, y);
}
Box.Image = Image;

Obviously the panel in this case is useless but I simply copied the
layout from the main code--in the main code there are some controls
off to the side and I use the panel to make the picture box take up
the whole form.

This code *SHOULD* draw one half of the screen with vertical lines and
one half with horizontal. I'm getting a gray mass on the left and the
expected behavior on the right.

For what it is worth, I see what you say it *SHOULD* draw when I execute
your routine.

On Wed, 04 Nov 2009 20:40:56 -0500, Family Tree Mike
FamilyTreeMike at (no spam) ThisOldHouse.com> wrote:

Loren Pechtel wrote:
On Wed, 04 Nov 2009 12:30:56 -0800, Peter Duniho
no.peted.spam at (no spam) no.nwlink.spam.com> wrote:

This code *SHOULD* draw one half of the screen with vertical lines and
one half with horizontal. I'm getting a gray mass on the left and the
expected behavior on the right.
For what it is worth, I see what you say it *SHOULD* draw when I execute
your routine.

What in the world is the difference then? How do I get it to draw
what you're seeing?

What in the world is the difference then? How do I get it to draw
what you're seeing?

There should be no scaling in my case [...]

Loren Pechtel wrote:
On Wed, 04 Nov 2009 20:40:56 -0500, Family Tree Mike
FamilyTreeMike at (no spam) ThisOldHouse.com> wrote:

Loren Pechtel wrote:
On Wed, 04 Nov 2009 12:30:56 -0800, Peter Duniho
no.peted.spam at (no spam) no.nwlink.spam.com> wrote:


snip


This code *SHOULD* draw one half of the screen with vertical lines and
one half with horizontal. I'm getting a gray mass on the left and the
expected behavior on the right.
For what it is worth, I see what you say it *SHOULD* draw when I execute
your routine.

What in the world is the difference then? How do I get it to draw
what you're seeing?

I suspect screen settings. When I set my display settings really
poorly, then I see what you observe. My normal settings are 1680x1050
32 bit color.

Loren Pechtel wrote:
What in the world is the difference then? How do I get it to draw
what you're seeing?

You've yet to establish it's _not_ drawing what Mike is seeing.

Visual inspection isn't good enough. Just because you've drawn a bitmap
a certain way, that's no guarantee it will be presented on the screen
that way.