shadow getting darker drawn on bitmap
I'm trying to create a shadow to a rectangle drawn dynamically on a bitmap. The problem is the shadow gets darker each time I draw a new rectangle (please see screenshot). I suspect that the same bitmap is used to draw the new rectangles. I tried using Graphics.clear() but it cleans the screen which I don't want.
How can solve this problem? Here is the code which draws the shadow:public void drawAll(Rectangle baseRect,Graphics g)
{
int shadWidth = 10;
Bitmap bm = new Bitmap(shadWidth, baseRect.Height+shadWidth);//baseRect is created dynamically
for (int y = 0; y < baseRect.Height + shadWidth; y++)
{
int factor = 255 / shadWidth;//255 is the alpha color divided over the shadow width
int alpha = 255;
for (int x = 0; x < shadWidth; x++)
{
alpha -= factor;
i开发者_运维知识库f (alpha < 0) alpha = 0;
Color transColr = Color.FromArgb(alpha, 0, 0, 0);
bm.SetPixel(x, y, transColr);
}
}
GraphicsPath path = new GraphicsPath();
PointF[] pts = new[] {new PointF(baseRect.Right, baseRect.Top),
new PointF(baseRect.Right+shadWidth, baseRect.Top+shadWidth),
new PointF(baseRect.Right+shadWidth, baseRect.Bottom+shadWidth),
new PointF(baseRect.Right, baseRect.Bottom),
new PointF(baseRect.Right, baseRect.Top)};
path.AddLines(pts);
SmoothingMode old = g.SmoothingMode;
g.SmoothingMode = SmoothingMode.AntiAlias;
g.DrawImageUnscaled(bm, baseRect.Right, baseRect.Y);
}
精彩评论