to read bmp files we may use this http://msdn.microsoft.com/en-us/library/dd183376(VS.85).aspx
as the header file and then get rgb triplets. How to get the rgb triplets of jpeg file, is there any such header file available. Please share the link if any.
The JPEG file format does not store the rgb triplets directly but it uses some sort of image compression. The file actually contains blocks of 64 (if I remember correctly) pixels which are attributed with a cosine pattern defining the actual colors.
You really should use a library (libjpeg, imagemagick, gd, ... e.g., depending on your use case) to read and decode the files and generate the rgb triplets in memory.
According to the answer to this question on MSDN, you could use the GDI+ component, which can load not only BMP, but JPG and other image formats too. From it, you will get a memory bitmap.
Here is an example on how to do that.
Check this library: libjpeg. This library implements JPEG image encoding, decoding,
and transcoding.
Related
I want to write a script to extract the PixelDATA of a DICOM file using c or c ++, I don't want to use external libraries like dicomsdl... if anyone can help me to write algorithm for extract and show image .
Just extracting the image data under the pixel data is not enough to interpret the DICOM image properly. You will need other attributes from DICOM file such as Rows, Columns, Bit Allocated, Bit Stored, High Bit, Photometric Interpretation, Sample Per Pixel to Number of Frames information just to interpret the raw uncompressed image data. Also, stored image data can be in Little Endian or Big Endian byte order. In addition, image data can be encapsulated or compressed (e.g. compressed using different compression algorithms such as JPEG, JPEG 2000, JPEG LS, RLE etc)) and compressed streams are stored differently than the uncompressed image data. Even the PixelData element can exist in multiple locations in a single DICOM file (e.g. one under the Icon Image Sequence (thumbnail) and one at the top level (actual image).
It can get more complicated when you need to account for Palette Color (segmented vs un-segmented), modality LUT, VOI LUT etc. My recommendation is to use an existing DICOM SDK and there are many open source and commercial SDK available for different platforms and programming environments.
Is it possible to:
read an image given by just a filename (not knowing the image format) to a 2d matrix rgb uncompressed form (e.g. read an JPG to a 2d array)
access the bytes of that image, copy them, change them... (e.g. inverse the colors, I need a pointer to the image bytes, setters/getters won't do )
save those bytes to any given image format (e.g. save the inversed image to PNG)
Is it possible with boost::gil ? Maybe there is a different library more appropriate for such a task?
Sample code would be highly appreciated.
Yes, you can do all that in boost::gil.
What you should know though, is that boost::gil is only a universal interface and doesn't handle reading/writing images all by itself. You still need to use a second library, e.g. libpng..
Yes, yes and yes.
There are functions that enable you to read and write JPEG, TIFF and PNG images: see here.
For the second bullet, it is what just GIL is meant to do. You can manipulate images using its facilities (click here).
I'm trying to extract all images out of PDF files in C++. I'm stuck in decoding CCITT encoded images.
Does anyone know an opensourced code for this?
I use the ImageMagick Magick++ Library, is it possible to do the decoding with this library, too?
Thanks for your help!
CCITT is one of the encodings TIFF supports, though in a PDF file the CCITT images are probably raw data.
You can convert a raw CCITT image into a Tiff image using Fax2Tiff. It should be easy enough to work with the image once it is encoded as a Tiff.
Fax2Tiff is part of LibTiff. See LibTiff Source
Or you can append a header on it and treat it as a tiff file.
I want a c++ Code to read every pixel from an image file. and i want to save the pixels like:
r[]
g[]
b[]
does somebody know how to do this?
The answer depends on the format of the image file. Is it a format which contains raw RGB data (such as uncompressed TGA)? Is it a YUV image? Is it a compressed image such as JPEG or PNG?
There are already plenty of C++ libraries out there which can read a wide variety of image file formats, and then provide the pixel-level access you require. Take a look at Adobe's GIL, or CImg for example.
There are many freely available libraries for reading different image file formats. Since you're using C++ you might want to look at Adobe's Generic Image Library (GIL) or even OpenCV.
This will sort you out, very easy to use and 'low level' image library:
http://easybmp.sourceforge.net/
Two libraries that I've used that jump to mind are:
ImageMagick
libGD
These libraries can handle a wide variety of image formats, depending on what you need.
I am having a bit of a problem.
I get a RAW char* buffer from a camera and I need to add this tags before I can save it to disk. Writing the file to disk and reading it back again is not an option, as this will happen thousands of times.
The buffer data I receive from the camera does not contain any EXIF information, apart from the Width, Height and Pixels per Inch.
Any ideas? (C++)
Look at this PDF, on page 20 you have a diagram showing you were to place or modify your exif information. What is the difference with a file on disk ?
Does the JPEG buffer of your camera contain an EXIF section already ?
What's the difference? Why would doing it to a file on the disk be any different from doing it in memory?
Just do whatever it is you do after you read the file from the disk..
As far as I know EXIF data in JPEG is continuous subpart of file.
So
prepare EXIF data in memory
write part of JPEG file upto EXIF
write prepared EXIF
write rest of JPEG file
You might want to take a look into Exiv2 library. I know it can work on files but I suppose it also has functions to work on memory buffers.