8/25/2023 0 Comments Win32 transparent rectangleThe bitmap is obtained from a tiff image, edited with Photoshop.ĪlphaBlend(*dp.pDC, outputOrigin.x, outputOrigin.y, m_bitmap.Width(), m_bitmap.Height(), memDC, 0, 0, m_bitmap.Width(), m_bitmap.Height(), bld) Īny insights will be very appreciated, thank you.Īctually, the Windows AlphaBlend function has variable speeds depending on the specific parameters it's given. It looks like the Alphablend adds with saturation the coresponding channels of the colors. I have a problem with the AlphaBlend function, that is the rendered bitmap doesn't look like it should.įor example, a bitmap with a pure red opaque region (a = 255, r = 255, g = 0, b = 0) and transparent in rest looks very weird: on a white background it's completly transparent, on a blue background the red region is magenta, etc. If in doubt, please contact the author via the discussion board below.Ī list of licenses authors might use can be found here. This article has no explicit license attached to it, but may contain usage terms in the article text or the download files themselves. See the sample application for a demonstration.Ījou University C.C. Set the SourceConstantAlpha value to 255 (indicates that the image is opaque) when you only want to use per-pixel alpha values. If you set SourceConstantAlpha to 0, it is assumed that your image is transparent. The SourceConstantAlpha value is combined with any per-pixel alpha values. MSDN states: The SourceConstantaAlpha member of BLENDFUNCTION specifies an alpha transparency value to be used on the entire source bitmap. SourceConstantAlpha must be between 0 (transparent) and 255 (semi-transparent).Wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) Wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) Wndclass.style = CS_HREDRAW | CS_VREDRAW Static TCHAR szAppName = TEXT ("AltWind") Int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, ![]() LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) Aside from the return value, PolyPolygon is functionally equivalent to the following code: The apt array has all the points for all the polygons. For each polygon, the aiCounts array gives the number of points in the polygon. The number of polygons it draws is given as the last argument. PolyPolygon (hdc, apt, aiCounts, iPol圜ount) (This does not happen with the Polyline function.) The PolyPolygon function looks like this: If the last point in this array is different from the first point, Windows adds another line that connects the last point with the first point. The apt argument is an array of POINT structures, and iCount is the number of points. The function call is similar to the Polyline function: Polygon is the sixth function for drawing a bordered and filled figure. I've already discussed the first five area-filling functions. The Polygon Function and the Polygon-Filling Mode You can also create customized brushes just as you can create customized pens. SelectObject (hdc, GetStockobject (NULL_BRUSH) If you want to draw the outline of the figure without filling in the interior, select the NULL_BRUSH into the device context: SelectObject (hdc, GetStockObject (NULL_PEN)) ![]() To draw a figure without a border, select the NULL_PEN into the device context: Now when you draw one of the figures listed above, the interior will be gray. You can select it into the device context by calling SelectObject: You can get the handle to the GRAY_BRUSH by calling GetStockObject: Windows defines HBRUSH to be a handle to a brush, so you can first define a variable for the brush handle: You can select one of the stock brushes into the device context the same way you select a stock pen. Windows defines six stock brushes: WHITE_BRUSH, LTGRAY_BRUSH, GRAY_BRUSH, DKGRAY_BRUSH, BLACK_BRUSH, and NULL_BRUSH (or HOLLOW_BRUSH). By default, this is the stock object called WHITE_BRUSH, which means that the interior will be drawn as white. The figure is filled with the current brush selected in the device context. Everything we learned about lines also applies to the borders around these figures. The current background mode, background color, and drawing mode are all used for this outline, just as if Windows were drawing a line. Windows draws the outline of the figure with the current pen selected in the device context. Pie wedge defined by the circumference of an ellipse Windows' seven functions for drawing filled areas with borders are listed in the table below.Īrc on the circumference of an ellipse with endpoints connected by a chord The next step up from drawing lines is filling enclosed areas. Drawing Filled Areas Drawing Filled Areas
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