I would like to process Landsat8 raw data with OCaml. The data is stored in TIF files. An example of such a file can be found here:
http://landsat-pds.s3.amazonaws.com/L8/139/045/LC81390452014295LGN00/LC81390452014295LGN00_B1.TIF
How can I read a TIF file in OCaml? Is there a library that already does this?
If you're working with a Landsat or other GeoTIFF image you may want to use bindings to GDAL for more complete support: https://github.com/hcarty/ocaml-gdal and http://gdal.org/
GDAL allows you to access the raw values and their geospatial information - location, projection and whatever else is included in the underlying TIFF.
I have not used it in many years, but there is a library named camlimages that claims to support TIF files. You can install it with OPAM.
Related
I'm trying to find a way to visualize a .trk file with C++ and VTK libraries but I don't understand if I need to convert the file to a format known by VTK or if exists a direct way to display it!
Any ideas or suggestions?
Vtk does not have reader for trackvis format. According to this https://www.nitrc.org/frs/shownotes.php?release_id=724 trackvis v >=0.5 can export vtk format.
I need to convert shapefiles (.shp) to .mdb file.
I tried to use GDAL libriary, but it supports only read operations on .mdb file, and It is why I cannot create a new .mdb source.
In the future I will need to automatize conversion by wrapping in .NET environment.
Do you have some experience in similar issues?
Is it possible to convert a PDF file to cv::Mat?
I know that PDF file is generally vector of objects, but given a required resolution. Is there any tool that can do such a conversion?
OpenCV doesn't support pdf format at all, so you should convert pdf page to image using another library. Read this discussion: Open source PDF library for C/C++ application?
Also this question is similar to yours: What C++ library can I use to convert a PDF to an image on windows?
Greetings all,
I am currently a rising Sophomore (CS major), and this summer, I'm trying to teach myself C++ (my school codes mainly in Java).
I have read many guides on C++ and gotten to the part with ofstream, saving and editing .txt files.
Now, I am interested in simply importing an image (jpeg, bitmap, not really important) and renaming the aforementioned image.
I have googled, asked around but to no avail.
Is this process possible without the download of external libraries (I dled CImg)?
Any hints or tips on how to expedite my goal would be much appreciated
Renaming an image is typically about the same as renaming any other file.
If you want to do more than that, you can also change the data in the Title field of the IPTC metadata. This does not require JPEG decoding, or anything like that -- you need to know the file format well enough to be able to find the IPTC metadata, and study the IPTC format well enough to find the Title field, but that's about all. Exactly how you'll get to the IPTC metadata will vary -- navigating a TIFF (for one example) takes a fair amount of code all by itself.
When you say "renaming the aforementioned image," do you mean changing metadata in the image file, or just changing the file name? If you are referring to metadata, then you need to either understand the file format or use a library that understands the file format. It's going to be different for each type of image file. If you basically just want to copy a file, you can either stream the contents from one file stream to another, or use a file system API.
std::ifstream infs("input.txt", std::ios::binary);
std::ofstream outfs("output.txt", std::ios::binary);
outfs << insfs.rdbuf();
An example of a file system API is CopyFile on Win32.
It's possible without libraries - you just need the image specs and 'C', the question is why?
Targa or bmp are probably the easiest, it's just a header and the image data as a binary block of values.
Gif, jpeg and png are more complex - the data is compressed
I need to get the image dimensions of a JPEG in C++. I'm looking for either a fairly simple way to do it or a smallish library that provides that functionality. I'm working in C++ on OpenVMS, so any external libraries may have to be adapted to compile on our systems - so please don't post me links to big, closed source libraries!
Has anyone come across anything that might do the trick, or understand the JPEG file format (I think I probably mean the JFIF file format here) to tell me how I might go about rolling my own solution?
You have this C function which may extract the relevant data for you.
This is a C routine but should compile fine with C++.
Pass it a normal FILE pointer (from fopen) to the beginning of a jpeg file and two int pointers to be set with the image height and width.
Or you may find in the Boost library a jpeg class which has the right function (From Adobe Generic Image Library).
jpeg_read_dimensions
boost::gil::jpeg_read_dimensions (const char *filename)
Returns the width and height of the JPEG file at the specified location. Throws std::ios_base::failure if the location does not correspond to a valid JPEG file.
libjpeg is reasonably small, open source and available on OpenVMS. It's probably quicker to install it than to handle JPEG yourself.
Maybe libjpeg?
You should be able to use this jpeg lib with this patch for OpenVMS
No need for full libjpeg library just to get this information (unless you need to do something else with the images). ImageInfo might help you. It is a Java class, but there are ports for other languages, including C++.
As pointed out, Exif might change these information (eg. with orientation setting).
You may want to try GDAL library which serves as an abstraction layer for large number of raster data formats, mostly used in geospatial applications for GIS/RS.
GDAL provides number of APIs, for C, C++ and scripting languages. Of course, it supports JPEG images and its variants like JPEG2000 and more.
Here is a very simple example how to open JPEG image and query its dimensions:
#include <gdal_priv.h>
GDALAllRegister(); // call ones in your application
GDALDataset* ds = (GDALDataset*)GDALOpen("my.jpeg", GA_ReadOnly);
int width = ds->GetRasterXSize();
int height = ds->GetRasterYSize(),
int nbands = ds->GetRasterCount();
Check GDAL API tutorial for more complete example.