I've done a bit of research but haven't found anything useful so far.
In short I would like to be able to create a bitmap/canvas in memory and use an api which has functions for drawing primitive shapes and text on that bitmap and read the memory directly. This should be completely done in memory and not need a window system or something like Qt or GTK.
Why? I'm writing for the raspberry pi and am interfacing with a 256x64 4 bit greyscale OLED display over spi. This is all working fine so far. I've written a couple of functions for writing text etc, but am wondering if there is already a library I can use. I double buffer the display so I just need to manipulate the image in memory and then read the entire picture in one.
I can easily do this in windows but am not sure the best way to do this in linux
I've used Image Magick to do similar things. It supports Bitmap and SVG. http://www.imagemagick.org/script/index.php
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while it seems such a basic question, I open this thread after extensive stackoverflow and Google search, which helped but not in a definitive way.
My C++ code draws to an array used as RGB framebuffer, hardware acceleration is not possible for this original graphics algorithm and I want my software to directly generate the images (no hardware acceleration) also for portability reasons.
However, I would like to have hardware acceleration to copy my C++ array into the window.
In the past, I have outputted to BMP files the images generated by my code, now I want to display them as efficiently as possible in realtime, on the screen's window.
I wrote a Win32 program that has a window freely resizeable by the user, so far so good.
What is the best / fastest / most efficient way to (possibly v-synched) blit/copy my system memory RGB array (I can adapt my graphics generator to any RGB format, so to avoid conversions) into the window that can change size any moment? (I am handling resizing via WM messages, and anyway I'm not asking how to resize/rescale the image array, I will do it all by myself, I mention resizeable window just to say that its size cannot be fixed after creation, but I will rescale it with my own code or, more precisely, I will simply reallocate the RGB array and generate a new image when the user changes the window's size)
NOTE: the image array should be allocated by my own program, but if having a system pointer will make things much more efficient (e.g. directly in video RAM) then it's ok.
Windows10 is the target OS, but at least Windows7 retro-compatibility would be better. Hardware is PC's, even low end, released in the last 5-10 years till now, so I guess all will have GDI hardware acceleration or such, like Direct2D or how is it called DirectDraw now.
NOTE: please do NOT propose the use of any library, I will have to deal directly with GDI calls, Direct2D or whatever is most efficient to do the task, but without using third-party libraries.
Thank you very much, I don't know much about Windows GUI coding, I've done console mode only until now, and some windows (thus I am familiar with WM messages) and basic DeviceContext graphics output. From my research (but I wanted to ask here because I'm in doubt really, and lotsa post I've read date back to 2010) SetDIBitsToDevice should be the best solution to my problem, but if so I think I would still need some way to synchronize with VSynch to avoid, if possible, the annoying tearing/flickering.
Need help with an interesting task. I need to write a C++ program that builds the graph and save a graphic file format bmp. I know how to initialize the bmp, but how to build a graph in it , I can`t think up. Necessary practical and theoretical help if there is a link to an article on the subject.
P.S. I apologize for my bad English :I
There are a lot of ways to do graphics in Windows. The lowest level and most fundamental is to use the Win32 APIs that employ the GDI (Graphics Device Interface), which is built in to Windows. With GDI calls you can paint anything to the screen, and the same GDI calls can be used to paint on an in-memory bitmap that is off screen. To get started in this direction search the net for Win32 tutorials.
I recommend FreeImage library (http://freeimage.sourceforge.net/) it's simple and fast lib without additional problems, you can manipulate graphic files dealing with them like 2D array.
And also, they have nice PDF document about API, you don't need tutorials to use it, just read API and you will get it. Also pr0tip: DON'T PUT SPACES BEFORE SPECIAL CHARACTERS LIKE ",!?.".
You might want to take a look at the graphviz package.
I'm just curious if there is a way to use OpenGL to write pixel data to an external JPEG/PNG/some other image file type (and also create an image to write the data to if one does not already exist). I couldn't really find anything on the subject. My program doesn't really make use of openGL at all otherwise, I just need something that can write out images.
Every image "put into" or "taken from" OpenGL is in a rather raw pixel format. OpenGL does neither have functionality for file I/O nor for handling of sophisticated image formats like e.g. BMP, JPEG or PNG, as that is completely out of its scope. So you will have to look for a different library to manage that and if this was the only reason you considered OpenGL, then you don't need it at all.
A very simple and easy to use one (and with an interface similar to OpenGL) would be DevIL. But many other larger frameworks for more complex tasks, like Qt (GUI and OS) or OpenCV (image processing) have functionality for image loading and saving. And last but not least many of the individual formats, like JPEG or PNG usually also have small official open-source libraries for handling their respective files.
I realize this question might be closed with the "not enough research". However I did spent like 2 days googling for it and didn't find a conclusive answer.
Well I have an application that spawns a window, not written in c++. This application can have a c-interface with dlls. Now I wish to use the power of OpenCV, so I started on a dll to extend. Ss passing image data from/to the application is near impossible (only capable of passing c-strings & double values directly - using the hard drive for drawing is slowing down too much for real time image manipulation).
I am looking into letting opencv draw the image data directly - onto the window. I can gain the window handle easily, so would it then be possible to let openCV draw their data "over" the other window - or better into the other window?
Is this even possible with any library (FFMPEG, or something else)?
Yes, it's possible, but it's far from ideal. You can use GDI to draw on top of the other window (just convert IplImage to HBITMAP). Another technique is to do such drawing in a borderless layered window.
An easier approach is, since you own both applications, to write a function that passes an IplImage between them using standard C data types, after all, IplImage is nothing but a data type that is built from these standard types.
Here is how you will disassemble IplImage into 5 standard parameters:
The size (int, int) of the image (width/height);
The (int) bit depth of the image;
The number (int) of channels;
And the (unsigned char*) pixels of the image;
After receiving these parameters on the other side, you may wonder: how do I assemble a IplImage from scratch? Call cvCreateImageHeader() followed by cvSetData().
Started up remote debugging a C++ project today on a Win 7 machine running in VMWare and was astonished to see the following pattern on a random memory location:
Who might code this (it's not me!) and for what reason?? Just curious if anyone has seen something like this.
It looks like a rendered mask for a font (each character in a font (typeface+size+style) is rendered once in-memory, then blitted to the output surface) using 8bpp, which suggests you've got font anti-aliasing enabled.
I'm assuming your project involves a GUI, you might be looking at a shared-memory area that GDI uses for storing rasterized fonts.
If not, then this might just be leftover memory from a previous process or OS component that wasn't zeroed before being used by your application.
It's hard to say. Possibly memory used to buffer some fonts (in this case, zeros), or even buffered printer or screen content.