int NewResX = 1280; <-- nueva resolucion
int NewResY = 1024;
DEVMODE displaymode;
int indice = 0;
displaymode.dmSize = sizeof(DEVMODE);
while (EnumDisplaySettings(NULL, indice, &displaymode))
{
if (displaymode.dmPelsWidth == NewResX && displaymode.dmPelsHeight == NewResY)
{
displaymode.dmFields = DM_PELSWIDTH | DM_PELSHEIGHT;
LONG result = ChangeDisplaySettings(&displaymode, CDS_TEST);
if (result == DISP_CHANGE_SUCCESSFUL)
{
ChangeDisplaySettings(&displaymode, 0);
break;
}
}
indice++;
}