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++.
Related
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.
If not, where can I find the algorithm to adjust contrast of an image. I will have to code it in C++ and have access to libjpeg and libjpeg-turbo libraries
http://en.wikipedia.org/wiki/Image_editing#Contrast_change_and_brightening
Is this a good starting point for color images?
The simplest I could have think of is the ImageMagick library, or do it yourself*.
* I know that the code in that answer is not c++, but if you know c or c++, you should be able to understand it.
You might like this one for starters: Processing in the 8-bit YUV Color Space
C there is the contrast adjustment. With an image with pixel format in YUV color space, constrast adjustment is quite easy and is an update for Y component of the pixel.
libjpeg is not quite the tool for image processing, unless you are decoding/encoding JPEGs and you need some processing on the way.
I'm building a program to convert an image file (whatever file type would be easiest) to G-Code for use on a rep-rap with a pen plotter attachment.
I'm wondering if i wanted to process the image pixel by pixel and check things like pixel color, how could I do this with C++?
I would really like to know how I can process a bitmap image, pixel by pixel, to check the color of the pixel.
The best way is to use a library, like for example Magick++.
When you load an image, you can access it's pixels data with Blob
You will probably want to use an existing library that has been tested.
But for fun/practice/etc, this would be a good exercise and wouldn't be impossible to do. The Bitmap Format is (relatively) simple compared with other image formats. The Wikipedia page has some tons of info, including some C++ code. It looks like once you've gotten past the header information, you get to a pixel array that shouldn't be difficult to parse.
Good luck.
Most image formats consist of a header and the actual raw image data. A bimpap image is no different. If you don't want to use one of the existing libraries, or if you are not allowed to, you should read about bitmap format :
http://en.wikipedia.org/wiki/BMP_file_format
Once you understand this you could create appropriate structs/classes to store the information you want from the header such as x,y size, bpp etc. And also have a pointer to the raw image data. You could then simpy iterate through every pixel and do whatever you want with it :)
Once you decipher the image file, I suggest you place the pixels into a matrix, for the first pass. (Future revisions can use other methods to access the pixels).
You can apply transformations to the pixels by using matrix multiplication. You can also access the pixels individually by using array indexing.
Search the web and SO for "introduction to graphics c++".
I am looking for a method, software or library for simple image analysis.
The input image will be a white-colored background, and some random small black dots on it.
I need to generate a .txt file that represents these dots' coordinates. That is, if there are three dots in the image the output will be a text file that includes somehow a representation of three coordinates, (x1,y1), (x2,y2), and (x3,y3).
I have searched the web for hours and didn't find something appropriate, all I found was complex programs for image processing.
I've been told that it's easy to write code for this mission in MATLAB, but I'm unfamiliar with MATLAB.
Can this be done easily with C++, Java or C#?
Any good libraries?
It is quite simple in any language. Depending on the form of your input, you probably need to go over all of it (assuming it is a simple matrix - simply have two nested loops, one for the x coordinate and one for the y coordinate), whenever you encounter a black dot - simply output the current indexes which would be the x and y coordinates for the dot.
As to libraries, anything other than something to decode your input to the form of such a matrix (e.g. a JPEG decoder) would be overkill.
I don't think you would need image processing libraries for this kind of problem (somebody correct me if I am wrong) since these libraries may focus on image manipulation and not recognition. What you will need is a knowledge of the image format that you are supporting (how are they stored, how are they interpreted, etc) and basic C file system functions.
For example, if you are expecting a JPG file format you will simply calculate the padding for each scanline and reach each scan line one by one, and each pixel in the line one by one. You'd have to use two counters, one for the row and one for the column. If the pixel is simply not white, then you have your coordinate
This is something which should be very easy for you to do without any external software; something like
for(y in [0..height]) {
for(x in [0..width]) {
if(pixels[y][x].color == BLACK)
print("(%d, %d)", x, y);
}
}
would work.
The bitmap file format is quite easy to read.
http://en.wikipedia.org/wiki/BMP_file_format
You could just stream the bytes into an array using this info. I've written a few BMP readers; it is a trivial matter.
Also, although I cannot vouch for its ease of use as I've never used it before, I've heard that EasyBMP works fine too.
CImg library shold help you. From CImg FAQ:
1.1. What is the CImg Library ?
The CImg Library is an open-source C++ toolkit for image processing.
It mainly consists in a (big) single header file CImg.h providing a
set of C++ classes and functions that can be used in your own sources,
to load/save, manage/process and display generic images. It's actually
a very simple and pleasant toolkit for coding image processing stuffs
in C++ : Just include the header file CImg.h, and you are ready to
handle images in your C++ programs.
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.