Simple bitmap graphics in c++? - c++

Question

I'm a Flash programmer and I'm currently exploring C++. In flash, you can create a bitmap and place it on the screen, and then use methods like getPixel(x, y), setPixel(x, y, c) ect. Press ctrl+enter and you can get started with what ever you want to do.
I use Visual C++ 2010. Since I've used Flash alot I'm used to simple and short commands. In C++ though, it's harder to figure out how to get a bitmap where you can manipulate pixels.
I don't know much about graphics enginges or 3D engines, it would be very useful information, but first I'd like to see what I can create with pixels, so do you know a simple way to create a manipulatable bitmap in C++? As optimized as possible, then I can write my own drawLine, drawCurve ect functions. :)

Answer 1

Because you mentioned Visual C++ 2010, I will assume that you are using Vista or higher and you want to first draw 2D graphics using the native Windows C++ approach. If this is the case, you want to use Direct2D. You may find old articles that use GDI, but this is the old way, so don't use it. Here is the link to MSDN introducing Direct2D.

Answer 2

If you really want to use C++ you should look at using GDI+ which is the standard windows/VS way of doing graphics. This is a slight highter level (friendlier) api than the older GDI api for doing graphics that dates back to (pre?) MFC days. You will need to get a basic grasp of device contexts etc... in order to understand how to load your bitmap from a file and get it on the screen.
CGI+ allows easy manipulation of a bitmap on a per pixel basis using the LockBits method. It can read most common image formats (bmp, jpg, png etc).
The example code below shows a typical load bitmap and read some pixels type code (it is taken verbatim from this msdn gdi+ article
#include <windows.h>
#include <gdiplus.h>
#include <stdio.h>
using namespace Gdiplus;
INT main() {
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
Bitmap* bitmap = new Bitmap(L"LockBitsTest1.bmp");
BitmapData* bitmapData = new BitmapData;
Rect rect(20, 30, 5, 3);
// Lock a 5x3 rectangular portion of the bitmap for reading.
bitmap->LockBits(
&rect,
ImageLockModeRead,
PixelFormat32bppARGB,
bitmapData);
printf("The stride is %d.\n\n", bitmapData->Stride);
// Display the hexadecimal value of each pixel in the 5x3 rectangle.
UINT* pixels = (UINT*)bitmapData->Scan0;
for(UINT row = 0; row < 3; ++row) {
for(UINT col = 0; col < 5; ++col)
printf("%x\n", pixels[row * bitmapData->Stride / 4 + col]);
printf("- - - - - - - - - - \n");
}
bitmap->UnlockBits(bitmapData);
delete bitmapData;
delete bitmap;
GdiplusShutdown(gdiplusToken);
return 0;
}
As for draw line, draw curve etc routines - these are all found on the Graphics object in GDI+. Its the main object that sits between your code and the screen. A Graphics object would be used to render the above bitmap using Graphics.DrawImage.

Answer 3

Well the answer that is about to come is probably one you won't like, but I'll give it anyways :)
C++ has no notion of graphics output at all. Luckily, we have gotten a standardized way of printing text to the screen - but thats it. Really. No joking here.
However, most operating systems provide a means of graphics output (mostly via a C interface, as C is binary compatible to almost everything), and there are also C++ wrapper libraries that incorporate access to those. Dealing with OS issues is, however, a very different beast than C++ is (and thats kinda beast, I can tell ;).
Luckily, if you don't want to/have to understand the full story, I can recommend Qt (http://qt.nokia.com/products/) as a very decent library for GUI programming. And once you have a GUI window, you will also have the possibility to draw a bitmap into that GUI (I believe Qt has direct bitmap support and also the possibility to load images).
However, I will have to refer you to the tutorial docs of Qt, as even a simple introduction would go way over what would be a still understandable forum answer.
And this, I'm afraid, will be as easy as it can get drawing something onto the screen using C++. Nowhere near the simplicity of Flash for that purpose but in the end way more powerful.
Good luck.

Answer 4

You need external library to read images from file. Two libraries I like are SDL_image and stb_image. Both give you image in a format that lets you access and manipulate pixels.
Also to display the image you will need external library. SDL is popular and simple one.

Answer 5

Use PixelToaster if you just want easy access to a framebuffer.