I want to read the contents of every pixel in an image i have and convert it to a bit-stream (raw bits) or contain it in a 2-D array . Which would be the best place to start looking for such a conversion?
Specifics of the image : Standard test image called lena.bmp
size : 256 x 256
Bit depth of pixel : 8
Also I would like to know the importance of the number of bits per pixel with regards to this question since packing and unpacking will also be incorporated .
CImg is a nice simple, lightweight C++ library which can load and save a number of image formats (including BMP).
It's a single header file, so there's no need to compile or link the library. Just include the header, and you're good to go.
You should investigate OpenCV: a cross-platform computer vision library. It provides a C++ API as well as a C API, and it supports many image formats including bmp.
In the C++ interface, cv::Mat is the type that represents a 2D image. A simple application that loads and displays an image can be found here.
To learn how to access the matrix elements (pixels) you can check these threads:
OpenCV get pixel information from Mat image
Pixel access in OpenCV 2.2
Common Matrix Operations in OpenCV
OpenCV’s C++ interface offers a short introduction to cv::Mat. There has been many threads on Stackoverflow regarding OpenCV, there's a lot of valuable content around and you can benefit a lot by using the search box.
This page has a collection of books/tutorials/install guides focused on OpenCV, but this the newest official tutorial.
Related
I am trying to perform text image restoration and I can find no proper documentation on how to perform OMP or K-SVD in C++ using opencv.
I have over 1000 training images of different sizes so do I divide images into equal sized patches or resize all images? How do I construct the signal matrix X?
What other pre-processing steps are required for sparse coding? How to actually perform K-SVD on color images?
What data type is available in OpenCV for an image dictionary and how do I initialize the Dictionary D?
I have these very basic questions and have tried to use various libraries but they don't make the working very clear.
I found this code useful. This is the only implementation in opencv I have come across so far. I guess it uses a single image for dictionary learning whereas I have to use at least 1000 images. But it certainly provides a good guideline.
I'm trying to make a C++ console app that can convert binary(mp3) files to images. How can I read every binary character in the file, convert to hex, and then save it as an image. Here is what I want but in C++
You might find this tutorial helpful:
http://www.cplusplus.com/doc/tutorial/files/
(Scroll down to the section binary files)
Also, let me share my standard recommended links for people asking for aid on basic c++:
Full scale tutorial on c++
C++ Language Reference (including STL)
ANSI C Language reference for all those pesky C stuff that C++ keeps using
Create an image with an area big enough to fit the data in.
For each byte in the source file, set a pixel. You could do this a number of ways - monochrome, or take bytes in threes and write them as red, green and blue for a 24-bit colour image.
Save the image to disk, e.g. in PNG format using libpng.
If you want a more specific answer, you'll need to ask a more specific question.
I want to use a CUDA-enabled SIFT library but I am using the OpenCV driver to get images from the webcam? The Cuda library is using the Devil Library for image data types.
Should I transform the images from OpenCV data types to Devil? Or Should I use another method for getting images from the webcam[devil compatible data types]?
I am not familiar with the DeviL but from the manual it states that it supports the following formats:
IL_COLOUR_INDEX
IL_RGB
IL_RGBA
IL_BGR
IL_BGRA
IL_LUMINANCE
of varying bit depths.
When loading images, OpenCV also supports most of these image types and bit depths and conversion between them is pretty straightforward (see the convertTo() function in the openCV documentation) . Using a webcam may be more complex.
It is difficult to answer your question directly without knowing the interface of the specific library. If the library accepts a devil image in a specific form, then it is likely you will have to give it in that form. OpenCV will likely be able to output data in the required form; if not, you may have to write code to transform it yourself.
I want to process an image in C++. How can I access the 3D array representing the JPEG image as is done in MATLAB?
I'd suggest using OpenCV for the task; C++ documentation is available here. The relevant (I believe) data structure which you'd have to use is the Point3_ class, which represents a 3D point in the image.
Well, I've never used MATLAB for such a task, but in C++ you will need some JPEG loader library like OpenIL or FreeImage. These will allow you to access the picture as byte arrays.
FreeImage's FreeImage_GetBits function has a detailed example in the documentation on how to access per pixel per channel data.
BTW, if you plan to do image processing in C/C++, I'd suggest you to check out the Insight Segmentation and Registration Toolkit and OpenCV.
How can I do simple thing like manipulate image programmatically ? ( with C++ I guess .. )
jpgs/png/gif .....
check out BOOST , it has a simple Image Processing Library called GIL. It also has extensions to import common formats.
http://www.boost.org/doc/libs/1_39_0/libs/gil/doc/index.html
Using .NET you have two options:
GDI+ from System.Drawing namespace (Bitmap class)
WPF engine wich can do a lot of things
If you want low level processing you can use unsafe code and pointers.
A Bitmap or Image is just a big array of bytes.
You need to learn:
what is a stride (extra padding bytes after each row of pixels)
how to compute the next row or a specific pixel location using width, height, stride
the image formats RGB, ARGB, white&black
basic image processing functions (luminosity, midtone, contrast, color detection, edge detection, matrix convulsion)
3D vectorial representation of a RGB color
Depending on how fancy you want to get, you may want to look at OpenCV. It's a computer vision library that has functions ranging from reading and writing images to image processing to advanced things like object detection.
Magick++ is a C++ API for the excellent ImageMagick library.
An advantage of ImageMagick is that it can be used from the command-line and a bunch of popular scripting and compiled languages too, and some of those might be more accessible to you than C++.