in a C++ MFC application. using the dc of ( CPaintDC dc(this);
)
How do i draw a rectangle ( LPRECT
) with an alpha transparency that i can adjust.?
Following is an example c# code which i need to convert into C++
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
Graphics g = e.Graphics;
Color color = Color.FromArgb(75,Color.Red); //sets color Red with 75% alpha transparency
Rectangle rectangle = new Rectangle(100,100,400,400);
g.FillRectangle(new SolidBrush(color), rectangle); //draws the rectangle with the color set.
}
You need to look into GDI+. Its a bit of a faff but you can create a "Graphics" object as follows:
Gdiplus::Graphics g( dc.GetSafeHdc() );
Gdiplus::Color color( 192, 255, 0, 0 );
Gdiplus::Rect rectangle( 100, 100, 400, 400 );
Gdiplus::SolidBrush solidBrush( color );
g.FillRectangle( &solidBrush, rectangle );
Don't forget to do
#include <gdiplus.h>
and to call
GdiplusStartup(...);
somewhere :)
You'll notice it's pretty damned similar to your C# code ;)
Its worth noting that the 75 you put in your FromArgb
code doesn't set 75% alpha it actually sets 75/255 alpha or ~29% alpha.
GDI (and thus MFC) has no decent support for drawing with an alpha. But GDI+ is available in C++ code as well. Use #include <gdiplus.h>
and initialize it with GdiplusStartup(). You can use the Graphics class, create one with its Graphics(HDC) constructor from your CPaintDC. And use its FillRectangle() method. The SDK docs are here .
int StartHoriz,StartVert,BarWidth,BarHeight; // rect start, width and height
StartHoriz=0;
StartVert=100;
width = 100;
height=120;
CDC* pCDC = GetDC(); // Get CDC pointer
CRect Rect(StartHoriz,StartVert,BarWidth,BarHeight); //create rectangle dimensions
pCDC->Rectangle(Rect); //draw rectangle
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.