c++ draw images on bitmap and save - c++

Question

//background feel free to skip
I am creating a animated clock for my Windows desktop background. Basically I create a bmp image with code using pre-drawn images (the numbers of the clock) then a save the bmp image and set the desktop background to that image. I tried using c# and .Net but inorder to set the desktop background I have to call a WinApi function (SystemParametersInfo). Calling this function from c# takes almost a second. Too long for an animation.
So now I want to do the same except in c++, I hope calling SystemParametersInfo will be faster from unmanaged code. EDIT:I used c# to create the bmp and c++ to set the desktop background and it is faster
//the question
I created a Win32 console project using Visual Studio 2012, and I managed to embed the pre-drawn images as resources. Now I need to combine the images onto a single bitmap and save it to the hdd. It has been four years since I last programmed in c++ so I have no idea how to draw a image and save it.
The code I found when googling all have to do painting to the screen, which I obviously don't want to do.
So how do create a bitmap, draw a resource image (also a bitmap) on it, and save it all in c++?
Thanks for any assistance.

Answer 1

This question is more about Windows API than about C++.
If you want to use Windows API, refer to GDI+:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms533798.aspx
.NET Framework wraps GDI+, so classes may be familiar for you just in C++ and not in C# with manual memory management, etc.
There are also some other libraries that can manipulate images. Personally me like GD, a C-style images manipulation library with many languages bindings.
https://bitbucket.org/libgd/gd-libgd/downloads
However, as always with Open Source, you will have to build it youself togeather with dependencies. So, probably GDI+ is the best.

Answer 2

As it turns out Win32 (c++) code is quick at changing the desktop background (under 20ms on i5 3.2ghz), where as the managed C# code takes anywhere from 500 to 3000ms. However, the unmanaged c++ code takes forever to draw the image (300 to 1500ms). So what I did was make two programs that work together. The managed C# program creates the image (under 20ms) and then saves it. The unmanaged c++ sets the saved image as the desktop background.
C#
static void Main(string[] args)
{
//the images positions where calculated manually and hard coded
//first image positoon
//X:532
//Y:335
Bitmap TheImage = new Bitmap(1366, 768);
Graphics G = Graphics.FromImage(TheImage);
DateTime DTNow = DateTime.Now;
while (true)
{
//get the time
DTNow = DateTime.Now;
//draw the canvas
G.DrawImage(Resources.canvas, 0, 0,1366,768);
//draw the first image of the hour
G.DrawImage(GetImage(DTNow.Hour,0),532,330,174,217);
//draw the second image of the hour
G.DrawImage(GetImage(DTNow.Hour, 1), 711, 330, 174, 217);
//draw the colon
if (DTNow.Second % 2 == 0) G.DrawImage(Resources.aColon, 890, 365,57,147);
//draw the first digit of the minute
G.DrawImage(GetImage(DTNow.Minute, 0), 952, 330, 174, 217);
//draw the second digit of the minute
G.DrawImage(GetImage(DTNow.Minute, 1), 1131, 330, 174, 217);
//save the file
try
{
File.Delete("C:\\background.bmp");
TheImage.Save("C:\\background.bmp", ImageFormat.Bmp);
}
catch
{
}
//calculate sleep time and sleep until next second
DTNow = DateTime.Now.AddSeconds(1);
DateTime NextSecond = new DateTime(DTNow.Year,DTNow.Month,DTNow.Day, DTNow.Hour,DTNow.Minute, DTNow.Second,500);
DTNow = DateTime.Now;
System.Threading.Thread.Sleep((int)NextSecond.Subtract(DTNow).TotalMilliseconds);
}
}
static Bitmap GetImage(int Number, int Index)
{
string NS = Number.ToString();
if (NS.Length < 2) NS = "0" + NS;
char[] digits = NS.ToCharArray();
switch (digits[Index])
{
case '1': { return Resources.a1; }
case '2': { return Resources.a2; }
case '3': { return Resources.a3; }
case '4': { return Resources.a4; }
case '5': { return Resources.a5; }
case '6': { return Resources.a6;}
case '7': { return Resources.a7;}
case '8': { return Resources.a8;}
case '9': { return Resources.a9; }
default: { return Resources.a0; }
}
}
}
c++
int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, char*, int nShowCmd)
{
while(true){
SystemParametersInfo(SPI_SETDESKWALLPAPER,0, L"C:\background.bmp", SPIF_UPDATEINIFILE);
int MS = (int)(((long)floor((long)clock()/(long)CLOCKS_PER_SEC)*1000l+1000l)-((long)clock()));
if(MS<=1000 && MS>0){
std::this_thread::sleep_for(std::chrono::milliseconds(MS));
}
else
{
}
}
return 0;
}