Develop Reference

Print a Form at higher dpi than screen resolution

Problem:
We need help with how to use WinForms' ability to auto-scale to different DPI’s to allow us to print our Forms at 600dpi, rather than at the screen DPI.
For What-You-See-Is-What-You-Get printing, we have been simply taking our nicely laid out window and printing it (turning off scrollbars and buttons and such). That works great EXCEPT for one thing: it comes out at 96dpi or 120dpi (whatever is the screen resolution)… either of which look grainy and unprofessional (our customers are complaining). And although it is as readable as what would be on the screen, you expect printed documents to be MORE readable than on-screen… you expect to be able to see additional details, to be able to read smaller text, etc.
Alternatives considered:
Given we have auto-scaling working great, such that our window looks good in 96dpi, 120dpi, 144 dpi, etc., we were hoping we could just draw our window at 600dpi and then print that.
OR, we looked at drawing the window off-screen 5-6x larger than normal such that we have the same number of pixels as 600dpi, but at 96 or 120 dpi… but then drawing that giant window to the printed page at 300 or 600 dpi (whatever the printer is).
If you can tell us how to do either of those alternatives, OR if you can give us a different way to accomplish our goal, then we would greatly appreciate it.
Current code:
In case it matters, our Form consists of a FlowLayoutPanel laying other smaller FlowLayoutPanels into columns, those smaller FlowLayoutPanels laying out a single column of TextBoxes, RichTextBoxes, a third-party RichTextEditor, PictureBoxes, and DataGridViews. We use a class derived from PrintDocument implementing OnBeginPrint, OnPrintPage, and OnEndPrint. In OnPrintPage, it manipulates our normal window off-screen (below and right of the actual screens) to fit the page size, then asks our main panel (the top FlowLayoutPanel) to DrawToBitmap, then uses the Graphics object passed into the PrintEventArgs to DrawImage that Bitmap. We also use Graphics.DrawString to apply a footer to each page. The main code:
using (Bitmap bm = new Bitmap(sz.Width, sz.Height))
{
Rectangle rect = new Rectangle(0, 0, sz.Width, sz.Height);
mp.DrawToBitmap(bm, rect);
e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; // so footer is anti-aliased
e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; // so when we scale up, we smooth out the jaggies somewhat
e.Graphics.DrawImage(bm, this.MarginBounds, rect, GraphicsUnit.Pixel);
if (this.Footer != null)
e.Graphics.DrawImage(this.Footer, this.FooterLocation);
if (!string.IsNullOrEmpty(pageNumber))
{
e.Graphics.DrawString(pageNumber, KBStyle.Normal.Font, Brushes.Black,
this.MarginBounds.X, this.FooterLocation.Y + FooterOffset);
}
}
How should we do this to get 600dpi to the printed page? (Or even 300 dpi would be great!)
When we print this, it looks far better when printed from a 120dpi machine than when printed from a 96dpi machine, hence why we know it is printing at screen resolution. But also makes us wonder if there’s some simple way to tell it “this Form should draw at 600 dpi” and then all the rest of the code above just works.
Note: if we grab an EMF (Enhanced Metafile) and print it to the printer in the code above, that EMF comes out at 600dpi. Unfortunately, we haven’t found a DrawToEMF method that we can call on the FlowLayoutPanel instead of DrawToBitmap. Changing the Bitmap to be 600dpi doesn’t help… the DrawToBitmap method still seems to draw the bitmap at screen resolution.
Thanks!!

Okay, I have figured this out... and it works great!
I still don’t know how to create a form at 300dpi and use the auto-scaling functionality.
BUT…
I have proven that if you create the window 3.125x larger than needed at 96 dpi, and scale the font up 3.125x, and so on, such that everything is the pixel count you’d need to be at 300dpi, even though your screen is at 96dpi, then you can use the normal Control.DrawToBitmap() functionality to turn that into a Bitmap, and then you can use the GDI Graphics.DrawImage(thatGiantBitmap, giantSrcRect, pageSizeDestRect) to the printer Graphics object, and it will map those giant 96dpi pixels to the page-size 300dpi pixels, giving you a 300dpi print. Perfect.
For any of our windows that support resizing AND let our users zoom the contents arbitrarily, then printing What-You-See-Is-What-You-Get is easy:
In OnBeginPrint of your PrintDocument, do:
(1) Optionally dup the Form so as to not mess with what the user is looking at
(2) Move the Form you want to print off-screen (below and right of all your screens)
(3) Set the Form so that it is allowed to grow bigger than the screen size (by default WinForms won’t grow larger than the screen)
(4) Divide 300 dpi by your screen dpi to get the growth factor
(5) Grow your Form by growth factor
(6) Zoom its contents by growth factor (if they don’t auto-scale / auto-zoom with the Form’s size)
In OnPrintPage of your PrintDocument, do:
(7) On whatever Control in your Form you want to print, do DrawToBitmap() to a Bitmap the size of that Control
(8) On the e.Graphics do DrawImage(thatGiantBitmap, giantSrcRect, pageSizeDestRect)
That DrawImage call will draw at the printer’s resolution, if you have that many pixels in your thatGiantBitmap. In this case, I computed the Bitmap to give the number of pixels needed for 300 dpi, so I will get 300 dpi print-outs even if the printer is 600 dpi. If you need full 600 dpi, just use 600 dpi in step 4's calculation.

Total guess here, but what about using CSS? I'm guessing at how much you want to scale, and don't know how you would know what scale the printer is.
Using the print media query makes this work for print but leaves the screen view alone.
#media print {
* {
transform: scale(2000px,2000px);
}
}

Why is WinForms drawing my image 4x the size?

I'm using WinForms to create a 512x512 px image with 96dpi resolution. After initialization, I use OnPaint to draw this image using Graphics.DrawImage. What I get as I run the program is the image shown below: essentially a 1024x1024 image which contains some jung vaguely resembling what I want to show, except it's made up of 2x2-pixel blocks all having uniformly identical colors. Which is weird.
Can someone help me figure out what is going on? This is only happening on high-DPI displays, the program works just fine on ordinary ones.
Update 1: I explicitly set the process to be DPI-unaware with SetProcessDpiAwareness(_Process_DPI_Awareness.Process_DPI_Unaware); and explicitly call DrawImage in a rectangle, i.e.,
e.Graphics.DrawImage(bmp,
new Rectangle(0, 0, 512, 512),
new Rectangle(0, 0, 512, 512), GraphicsUnit.Pixel);
and it did not help.
Edit 2: After turning DPI awareness on, I now get the same junk, but at the right size:
Edit 3: Finally got it, the artifacts were the results of my rendering things incorrectly on the CUDA side. The high-DPI nonsense was just a distraction.

This is only happening on high-DPI displays
That is entirely normal, you are seeing the image getting rescaled to match the DPI of the monitor. Which makes it bigger so the size in inches is the same.
The crude way to get this done is when you rely on DPI virtualization. Windows lets your program behave like it does on 96 DPI monitor, but gets it to draw into a bitmap. And rescales that bitmap to display it on the screen. Pretty crude, but your program is still usable, text quality suffers pretty noticeably.
The not-crude way is when you declared you program to be dpiAware. Now Windows no longer helps and it is Graphics.DrawImage() that takes care of the job. It by itself rescales the image to match the image DPI to the display DPI. Text looks very crisp. The image, meh, you have to move your chair back further.
If you don't want this rescaling to happen then you have to use the Graphics.DrawImage() overload that takes a Rectangle argument. But keep in mind that the image turns into a postage stamp on such a nice display. You'll have to move your chair closer :)

How to control Excel's scaling of bitmaps

I have a bitmap image and I want to put it in excel. I used this code I found here:
xlWorkSheet.Shapes.AddPicture("C:\\filesystem\\mb2.bmp",
msoFalse, msoCTrue, 0, 0, 518, 390);
But the resulting image is 1.333 times wider and higher. OK, so I can just multiply the dimensions by 0.75 and I get an image in excel with the desired dimensions.
xlWorkSheet.Shapes.AddPicture("C:\\filesystem\\mb2.bmp",
msoFalse, msoCTrue, 0, 0, (float)(518*0.75), (float)(390*0.75));
But that number 0.75 sitting there hard-coded really bothers me. Especially since I've seen this question in which the op's ratio is 0.76. Knowing that this code needs to run on any number of systems with different displays, I want to know how to get the ratio programmatically.
Somewhat also related to this question which has to do with copy-paste without code.

If you are talking about printing, the display is irrelevant.
The dimensions of the image need to be relative to the paper size. The size values in the AddPicture method are in points and are only loosely related to pixels. Points are units if measure that make sense to your printer. The application translates points to pixels for you so you don't need to worry about that.
You can use the InchesToPoints or CentimetersToPoints methods of the Application object to size your image to paper size.

How to stretch the video completely

I am using axWindowsMediaPlayer and when I make the screen full, video is being shown but the player put 2 black block near side of video. I don't want these blocks.
I tried
axWindowsMediaPlayer1.stretchToFit = true;
but that didn't work. Because my video is 800*600 and my screen 1920*1080, the problem might be. Any way to solve this problem programatically? I don't want to resize video.
Thanks in advance.

AxWMPlayer does not support nonuniform stretching. So, you have to either:
- make the WMPlayer of normal desired size, stretch uniformly (StretchToFit=true) and live with the black margins if they show up
- make the WMPlayer oversized in Height or Width (so that it sticks out of the target space), stretch uniformly (StretchToFit=true). Due to the oversized WMPlayer, some of the video will be trucated (displayed outside of the space) but also the black margins will be truncated
Those two ways will mantain aspect ratio.
If you don't need aspect ratio kept, you may apply some ScalingTransform (WPF) or another similar effect to stretch the view afterwards. You will need to calculate coordinates properly, but the fact that WMP always centers the video and that you can read the video dimensions from IWMPMedia helps much.

How do I position lines exactly in C#

I do NOT want the system trying to scale my drawing, I want to do it entirely on my own as any attempt to squeeze/stretch the graphics will produce ugly results. The problem is that as the image gets bigger I want to add more detail rather than have it simply scale up.
Right now I'm looking at two sets of stripes. One is black/white, the other is black/white/white. The pen width is set to 1.
When the line is drawn horizontally it's correct. The same logic drawing vertical lines appears to be doing some antialiasing, bleeding the black onto the nearby white. The black/white/white doesn't look as good as the horizontal, the black/white looks more like medium++ gray/medium-- gray.
The same code is generating the coordinates in all cases, the transform logic is simply selecting what offset to apply where as I am only supporting orientations on the cardinals. Since there's no floating point involved I can't be looking at precision issues.
How do I get the system to leave my graphics alone???
(Yeah, I realize this won't work at very high resolution and eventually I'll have to scale up the lines. Over any reasonable on-screen zoom factor this won't matter, for printer use I'll have to play with it and see where I need to scale. The basic problem is that I'm trying to shoehorn things into too few pixels without just making blobs.)
Edit: There is no scaling going on. I'm generating a bitmap the exact size of the target window. All lines are drawn at integer coordinates. The recommendation of setting SmoothingMode to None changes the situation: Now the black/white/white draws as a very clear gray/gray/white and the black/white draws as a solid gray box. Now that this is cleaned up I can see some individual vertical lines that were supposed to be black are actually doing the same thing of drawing as 2-pixel gray bars. It's like all my vertical lines are off by 1/2 pixel--yet every drawing command gets only integers.
Edit again: I've learned more about the problem. The image is being drawn correctly but trashed when displayed to the screen. (Saving it to disk and viewing it on the very same monitor shows it drawn correctly.)

You really should let the system manage it for you. You have described a certain behavior that is specific to the hardware you are using. Given different hardware, the problem may not exist at all, or it may exist horizontally but not vertically, or may only exist at much smaller or much larger resolutions, etc. etc.
The basic problem you described sounds like the vertical lines are being drawn "between" vertical stacks of pixels, which is causing the system to draw an anti-aliased line. The alternative to anti-aliasing the line is to shift it. The problem with that is the lines will "jitter" or "jerk" if the image is moved around, animated, or scaled or transformed in any other way. Generally, jerk is MUCH less desirable than anti-aliasing because it is more distracting.
You should be able to turn off anti-aliasing using the SmoothingMode enum, or you could try to handle positioning yourself. Either way, you are trading anti-aliasing for jittery, jerky rendering during any movement or transformation.

Have a look at System.Drawing.Drawing2d.SmoothingMode. Setting it to 'Default' or 'None' should turn off anti aliasing when doing line drawing. If you're talking about scaling an image without anti aliasing effects, have a look at InterpolationMode. Specifically, you might wish to set it to 'Nearest-Neighbor' which will keep your rectangular blocks perfectly crisp. Note that you will see some odd effects if you scale your image by anything other than whole numbers.

Perhaps you need to align your lines on half-pixel coordinates? A one pixel line drawn at say x = 5 would be drawn on the center of the line, which means it would go from x = 4.5 to x = 5.5. If you want it to go from x = 4 to x = 5 then you'd need to set its coordinate to x = 4.5.
GDI+ has a property: http://msdn.microsoft.com/en-us/library/system.drawing.graphics.pixeloffsetmode.aspx that allows you to control this behavior.

Sounds like you need to change your application to tell the system it is DPI aware so scaling doesn't occur. Here's an article on doing that: http://msdn.microsoft.com/en-us/library/ms701681%28VS.85%29.aspx