如何在纯gdi（不是gdi +）中填充圆角的渐变

Question

只是纯粹的gdi。 我们欢迎您的想法或代码。

Answer 1

创建圆角矩形作为路径，选择路径作为剪切路径，然后对同一矩形进行渐变填充。使用MFC的代码如下所示：

int top = 10;
int left = 10;
int right = 200;
int bottom = 200;
int radius = 20;


pDC->BeginPath();
pDC->RoundRect(left, top, right, bottom, radius, radius);
pDC->EndPath();
pDC->SelectClipPath(RGN_COPY);

TRIVERTEX vertices[2];

vertices[0].x = left;
vertices[0].y = top;
vertices[0].Red = 0xffff;
vertices[0].Green = 0;
vertices[0].Blue = 0;
vertices[0].Alpha = 0xffff;

vertices[1].x = right;
vertices[1].y = bottom;
vertices[1].Red = 0;
vertices[1].Green = 0;
vertices[1].Blue = 0xffff;
vertices[1].Alpha = 0xffff;

GRADIENT_RECT r;
r.UpperLeft = 0;
r.LowerRight = 1;

pDC->GradientFill(vertices, 2, &r, 1, GRADIENT_FILL_RECT_V);

如果您不使用MFC，则pDC->x(...)将替换为x(your_DC, ...)。