gdi

问题 Is there any way to set the style for the lineends for the TCanvas.LineTo method? It seems to default to rounded ends, which looks very bad for several lines in a row of different colours when Pen.Width is set to a large value (e.g. 9). It looks like this (rounded ends): ********........****** **********........****** **********........****** ********........****** (where * is e.g. blue and . is yellow) It is even worse if the two outer lines are drawn after the middle line: ********........*

问题 I am trying to calculate the pixel width of Excel columns, as described in this post, using the official formula from the OpenXML specification. However, in order to apply this formula, I need to know the Maximum Digit Width of the Normal font, which is the pixel width of the widest numeric digit. The OpenXML specification gives this example as a clarification: Using the Calibri font as an example, the maximum digit width of 11 point font size is 7 pixels (at 96 dpi). I have checked that this

问题 I have a set of points representing a line. It might be a closed shape or an open one. I need to draw a parallel line that goes besides the original one without any intersection. I have the following code to return the generated line. I have problems in the angles of the shape. Some point goes over the original line. My Code is: PointF[] GetParrarel(PointF[] lst, double width, float distance) { List<PointF> final = new List<PointF>(); width = width + distance; for (int i = 0; i < lst.Length-1

问题 I've been attempting to draw on an 8bpp grayscale bitmap without success. Here are some of my attempts. Maybe someone can point out what I'm doing wrong. =================================================== Attempt 1: Create, select, and draw: In constructor: CBitmap bm; bm.CreateBitmap (200, 200, 1, 8, NULL); In OnDraw: CDC *mdc=new CDC (); HGDIOBJ tmp = mdc->SelectObject(bm); Result: tmp is NULL, indicating failure. =================================================== Attempt 2:

问题 I'm trying to draw on the screen (the whole screen, on top of every other window) using GDI+. I've passed NULL to GetDC to get a HDC to the screen, and then used that to create a Graphics object, and used DrawRectangle to draw rectangles on the screen. Everything works..except...the inside of the rectangle won't update. Like if I draw it over a command prompt, and move the command prompt, the inside of the rectangle remains black. I expect to see whats under the rectangle. Here's the code

问题 I'm trying to draw on the screen (the whole screen, on top of every other window) using GDI+. I've passed NULL to GetDC to get a HDC to the screen, and then used that to create a Graphics object, and used DrawRectangle to draw rectangles on the screen. Everything works..except...the inside of the rectangle won't update. Like if I draw it over a command prompt, and move the command prompt, the inside of the rectangle remains black. I expect to see whats under the rectangle. Here's the code

问题 When I create a new Gdiplus::Bitmap using the Bitmap::FromHBITMAP function, the resulting Bitmap is opaque - none of the partial transparency from the original HBITMAP is preserved. Is there a way to create a Gdiplus::Bitmap from an HBITMAP which brings across the alpha channel data? 回答1: I think working code is more useful than instructions, so: #include <GdiPlus.h> #include <memory> Gdiplus::Status HBitmapToBitmap( HBITMAP source, Gdiplus::PixelFormat pixel_format, Gdiplus::Bitmap** result

问题 I have an HBITMAP containing alpha channel data. I can successfully render this using the ::AlphaBlend GDI function. However, when I call the ::GetPixel GDI function, I never get back values with an alpha component. The documentation does say that it returns the RGB value of the pixel. Is there a way to retrieve the alpha channel values for pixels in an HBITMAP ? I want to be able to detect when to use ::AlphaBlend, and when to use an old-school method for treating a particular colour in the

问题 I'm looking for the simple solution of how to convert the 32-bit bitmap to grayscale using GDI (not GDI+). Is there a possibility e.g. by changing the bitmap's pallete or something ? Of course there is plenty of examples in Delphi like this one, but I'm looking for a WinAPI function which would do this without iteration through the lines. 回答1: I haven't found any single GDI function doing this. The easiest way, as David mentioned in his comment, is to scan each line and compute the pixel

问题 I already know that sub-pixel positioning causes DirectWrite text rendering to be blurry compared to GDI. However, my question is a bit more fundamental: Why can't DirectWrite (and related methods) be made to render text as sharply as GDI? In other words: What prevents DirectWrite from being able to snap text to the nearest pixel, the way GDI can? Is it, for example, a hardware issue? A driver architecture issue? Is it simply not implemented? Or something else? Smaller sample: Larger samples: