GetPixel () SetPixel () execution efficiency

wangf91

Advice I have the following code to deepen the brightness of pixels in an area
The efficiency of actual execution is too slow.A better solution is required.

COLORREF rgb;
BYTE r, g, b;
for (UINT x = 0; x <xMax; x ++)
{
  for (UINT y = 0; y <yMax; y ++)
  {
    rgb = GetPixel (x, y);
    r = GetR (rgb);
    g = GetG (rgb);
    b = GetB (rgb);
    r + = 20; g + = 20; b + = 20; // The overflow problem need not be considered ... small hidden dangers ...
    SetPixel (x, y, RGB (r, g, b);
  }
}

bigbigcat

Do not display pixels one by one, display them together after modification in the memory

mac1234

Agree upstairs!
Cache it.

wangf91

Is the modified memDC

addforever

You can use GetObject to get the graphic data pointer, and then directly operate