I have applied JPEG baseline compression algorithm by writing each step in matlab. Now, I have the JPEG compresses image data in binary form and the header to be appended. Please tell me how to make a file that would be recognized as JPEG file by OS. Should it be binary file or what is the process.?
Regards
You are going to need to read two thing:
1) The JPEG standard
2) The standard for some file format (e.g., JFIF, EXIF).
You are going to need to have a JPEG file header (see file format standards). You are going to have to create DHT, DQT, SOF, and SOS markets for the compressed data (JPEG standard).
All of the data is in binary format. You have to remember to convert FF values in the compressed data stream to FFFF.
Related
I know ILNumerics handles mat file saved using -v6 or -v7.3 option quite nicely but anyone knows how to make it recognize files saved using -v7 option?
The -v7 option by default uses compression and hence ILNumerics will give me a message saying it does not support compressed file and suggests me using -v6 option to save the file.
I guess nowdays mat file saved using latest releases of matlab (like 2010 - 2014) prefer the -v7 file format against the -v7.3 format which internally uses HDF5 because of the overhead HDF5 causeds. And since compression it's also smaller in size than the -v6 file which also is a big advantage.
So can ILNumerics fill this gap? Or is there already a solution that I missed?
Thanks.
My MATLAB script generates a figure from a timeseries data that, when saved, is over 200 MB in size. Is there a way to compress the figure to a lesser size in '*.fig' format? The compression has to be lossless so that I can zoom in and view the details in the figure. The figure has to be saved in *.fig format so that the axis property relations between subplots are preserved and I can use the data cursor tool.
The *.fig format cannot be saved as is in compressed form. The format is just not capable of it. But in MATLAB you can use functions zip to compress files created by savefig, and unzip with passing to openfig. This way you can create simple script to load and save zipped figs. Of course you will need to use a temp file, which should be taken care of as well.
I have a binary file with .bin extension. This file is created by a data acquisition software. Basically a "measurement computing" 16-bit data-acquisition hardware is receiving signals from a transducer(after amplified by an amplifier) and sending this to PC by a USB. A program/software then is generating a .bin file corresponding received serial data from data aq. hardware. There are several ways to read this .bin file and plot the signal in MATLAB.
When I open this .bin file with a hexeditor I can see the ASCII or ones and zeros (binary). The thing is I don't know how to interpret this knowledge. There are 208000 bytes in the file obtained in 16 seconds. I was thinking each 2 bytes corresponds to a sample since the DAQ device has 16 bit resolution. So I thought for example a 16-bit data such as 1000100111110010 is converted by MATLAB to a corresponding voltage level. But I tried to open two different .bin files with different voltage levels such as 1V and 9V and still teh numbers do not seem to be related what I think.
How does MATLAB read and interpret binary digits from a .bin file?
Thnx,
Assuming your .bin file is literally just a dump of the values recorded, you can read the data using fread (see the documentation for more info):
fid = fopen('path_to_your_file', 'r');
nSamples = 104000;
data = fread(fid, nSamples, 'int16');
fclose(fid);
You will also need to know, however, whether this data is signed or unsigned - if it's unsigned you can use 'uint16' as the third argument to fread instead. You should also find out if it's big-endian or little-endian... You should check the original program's source code.
It's a good idea to record the sample rate at which you make acquisitions like this, because you'll be hard pressed to do anything but trivial analysis on it afterwards without knowing this information. Often this kind of data is stored in .wav files, so that both the data and its sample rate (and the bit depth, in fact) are stored in the file. That way you don't need a separate bit of paper to go along with your file (also, reading .wav files in MATLAB is extremely easy).
I have used video.MultimediaFileWriter to write frames from input AVI video file to an output AVI video file. After the output file is created the size of the output file is very large. I have used VideoCompressor's provided in MATLAB options. For example: for an input video size of 3.42MB after using compression techniques provided by MATLAB the output video size is 98.5MB.
Can anyone tell me how to bring the output AVI file to size of the input file?
The creation of videos using H.264 was added in R2012a. Older versions support the less efficient codecs MJPEG and DV, which probably explain your large files. However, this is not a major problem because you can recompress your videos using free tools, such as VirtualDub and x264. Here is a tutorial.
I would like to take a 512x512 image and convert it into a png byte array in Matlab so that I can stream it via a socket.
At the moment I take the array, write it to a png file using imwrite(I,'file.png'), then read it as a binary file and send it through the socket. This is obviously horribly inefficient because I first write to disk and then read from disk. I want to skip the and write to disk.
Is there anyway to do this in Matlab?
Probably not directly using the base MATLAB toolbox since the PNG file itself is created by the PNGWRITEC MEX-function. However, there may be some Java classes that can help, such as those in the javax.imageio package.