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.
Related
I need to read images in HDF5 format in my c++ code. I googled and it seems I can use ITK. Could you please let me know if there is such a possibility?
PS1. HDF5 images are in *.h5 format.
PS2. I'm using ITK to read images like png and jpg formats.
Thanks in advance,
I believe you can use ITK to read it. A good way to check whether your image file format is supported by the ITK's reader is to try opening your image using Slicer. If the file opens correctly, you are good to go.
If not, ITK might still read it as Slicer essentially only cares about 2D, scalar 3D and some special vector 3D cases.
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.
I'm trying to use the imwrite() OpenCV function. I want to save the frames with the .TIFF extension. The problem that I have is that the saved images are compressed so I can't use them. Any idea how I can escape this compression?
thanks in advance
Do not mind what sietschie says. The TIFF flag is hardcoded in the opencv binaries with a LZW compression. You can just turn this off (comment it out) or change it.
In:
3rdparty/libtiff/tiff.h
Remove this line:
#define COMPRESSION_LZW 5 /* Lempel-Ziv & Welch */
Then compile. Presto.
Tiff options other than that are automatically set (8 bit, 16bit, color, rgb, rgba,etc) depending on your image
According to the documentation OpenCV only exposes a limited set of options for writing image files.
Non of which belongs to TIFF-Files.
So unless you want to use your own function or modify the OpenCV source, this is not possible.
I would suggest using another uncompressed format for saving the frames like PXM or BMP, unless you have some specific reasons to use TIFF-Files.
cv::imwrite("imagen.TIFF", bayer, {cv::IMWRITE_TIFF_COMPRESSION, 1,
cv::IMWRITE_TIFF_XDPI, 72,cv::IMWRITE_TIFF_YDPI,72});
The simplest way is recompiling OpenCV or direct using libtiff, but I consider as not very good idea changing 3rdparty/libtiff/tiff.h: after this modification you can't save compressed TIFFs at all with OpenCV, and under non-windows systems you usually have separate libtiff (not as a part of OpenCV).
I suggest simpler approach (still OpenCV recompilation, but you save possibility of writing compressed tiff and don't change libtiff directly):
saving uncompressed TIFFs with OpenCV
Is this possible? It doesn't matter what format the image is, but I have to be able to open it, read pixel data into some sort of array, create a new image using a modified set of pixel data.
Thanks!
Boost.GIL has a good video tutorial which shows you how to read/write and process raw image data in a very generic, yet efficient, way.
You need code to encode and decode the formats you want to support. You can do this yourself (not really ideal/practical,) you can embed encoding/decoding libraries (like libpng, for example,) or you can embed image libraries like DevIL.
Boost seems to include some sort of image access library known as Boost.GIL. I really don't know much about it, though.
I suggest the TARGA image format for your needs. You just read/write a few values in a header, then the rest is an uncompressed array of RGBA pixel data. You won't even need Boost!
I suggest CImg. This library is extremely easy to use. You only have to include a header file in your code and set some parameters when compiling and that's it! I've used CImg with MingW and GCC.
I'm trying to use OpenCV to read/write images for me. Currently, I have them in a different, non-standard format, and I know how to get them into OpenCV's containers. Here are the requirements:
The pixels are 1, or 3 bands, U8, U16, U32, or F32
The images have metadata, random stuff, like the camera ID that took the images. I would like the metadata to be vi/notepad editable
I want to write as little code as possible when it comes to low level stuff. My experience is that this stuff requires the most maintenance.
I can define the format. It's only to read and write for these programs.
I don't want the pixels to be anything but binary, '0.5873499082' is way too much data for one float.
Is there a way to describe to OpenCV how to read and write image types it doesn't know? Are there image types already available for the types of images I have?
My interim solution is to use boost to serialize the image, and save the metadata in a separate file.
Try using gdal library for reading images and then convert it to IplImage.
OpenCV can't do that for you, you can store the metadata in a separate file, or you can use for example the jpeg exif (that won't be notepad editable though).