C++ :: Reading Stream Data From PDF Files Compressed In LZW?
Nov 28, 2013
I'm trying to read stream data from a stream in a pdf file compressed in LZW. My first step is to read this compressed data into a buffer. The second step is to decompress it. I know how to decompress it, it is the first step I am having trouble with.
How should I read this data? If I read each character into a char the numerical output will not exceed 256. LZW compressed output should exceed 256.
I read the pdf in binary mode and have tried the read function like below.
From what I understand (don't quote me), I should be reading in 12 bits at a time. Is that correct and if so should I be using a bitfield. If I do need a bitfield then how to I read the data from the stream into a bitfield of 12 bits without restricting the binary value of the characters being read from the compressed stream.
Code:
ifstream inputfilestream;
inputfilestream.open("myfile.pdf", ios::out | ios::binary);
char mychar; //unsigned char gives an error though it can be //converted to unsigned char later.
while (inputfilestream.read(mychar, 1)) {
// do something with the char.. I have stored it in an int vector
}
I have created TIFF Reader using libtiff in c++. Now I have many tiff files with old-style jpeg compression that has to be read/open using libtiff in c++.
I guess, as "old-style" JPEG compression is deprecated in TIFF, because it was never fully specified. And because of this under-specification, various vendors implemented it in different, incompatible ways. Support was dropped in favor for TIFF compression 7, JPEG.
Unfortunately,old TIFF files using this compression still exists.
#include<fstream.h> #include<conio.h> #include<string> class CLS { public : string name;
[code]....
I have used the above code to write the class instanc to a file "Text.txt"...But it seems that "f.write((char*)&c, sizeof(CLS));" is not working properly with string. The data can easily be written using stream object!
#include<fstream.h> #include<conio.h> #include<string> class CLS { public : string name;
[code]....
When I tried to read the data on the file...., it gave an error "Thread stopped...violation.."
I am writing a program to hide files behind other files using Alternate Data Streams in Windows NTFS file systems.
The program is as follows:
Code:
#include <stdio.h> #include <stdlib.h> int main(void){ char hostfile[75], hiddenfile[75], hiddenFileName[15] ; printf("Enter the name(with extension) and path of the file whose behind you want to hide another file: "); scanf("%75s", hostfile);
[Code]...
The complier is showing error as "Extra Perimeter in call to system" but I am not getting where?
I need make a CBitmap or a streamdata from a System.Windows.Controls::Image(rendered out put)in a SDI mfc application (supporting clr). Here is my codes:
Code: using namespace System; using namespace System::IO; using namespace System::Collections::Generic; using namespace System::Windows; using namespace System::Windows::Controls;
[Code] .....
By this codes i can read datastream from bitmapSource but in this way somthing goes wrong in most of GIF animations. After debug i found out i need 3 more things too decode a gif animation - (x,y) position and size of each frame and disposal method for each one - finally i just found a way to draw tru images on a form window by this codes:
Code: bitmapSource = decoder->Frames[0]; to Code: bitmapSource = decoder->Frames[01];
frame[1] has drawn perfectly on window(i think some how Image class takes care about - (x,y) position and size of each frame and disposal method for each one ),so im wonder if how can i make a CBitmap or a data stream from System.Windows.Controls::Image class to use in mfc app.
I wrote a program to write text contents to file stream through fputs, the file stream address was changed in the middle of writing text content to the stream (11% text content have been put into the file stream), that cause the file stream pointer can be evaluated problem and raise exception on stream validation code in fputs library function, my question is what things could go wrong to make file stream pointer changed its address to something else or a NULL pointer if the file stream have not been flushed and closed.
Issue 1: I am using a stringstream object in a block of my program that needs to be visited repeatedly depending on a user's selection from a menu. I want the contents of this stringstream object to be cleared any time control gets to this part of the program. I have tried the clear and flush functions to no avail.
Issue 2: I am reading data from a source text file that would be regularly changed during the course of program run. After the program run is over, I am supposed to save the results(which is basically the source text file AND all updates) in a destination file. This destination file would then serve as the source file when next the program is run. In other words, I want a scenario where my results overwrite the original contents of the source file; implying that my source and destination files are now one, pretty much. How can I do this?
I am trying to stream data to a file, and then return to the file to add further data. When I add data the second time, I then want to update the value of the second byte in the whole file. I can't seem to do this!
Here is my sample code:
Code: int a = 1; int b = 2; int c = 3; int d = 4; int e = 5; int f = 6; int g = 7; int x; fstream out1("file.dat", ios::out | ios::binary | ios::trunc);
[code]....
The output I get is "1, 2, 3, 4, 5, 6", but I want to be getting "1, 7, 3, 4, 5, 6", because in "out2", I seekp to the second integar entry, and change it to "7".
I have also tried using ios::ate in the constructor for "out2", but this gives me the out put "4, 7, 6, 6, 6, 6", which is suggesting that when I create my fstream object "in", any seekg commands are relative to the beginning of the "out2" stream, rather than the "out1" stream.
I have written the following code to add data to text files which are required to store 3D scan data (I have to calculate the y-coordinate). My code seems to work except that it stops working when I want to create more than ten text files i.e. the directory I am trying to store them in will not hold any more than ten text files. Code is shown below.
How do I read a .pdf file using C++? When I try to open it using myfile.open ("example.pdf"); but all I see is some Crazy Symbols. Is there any way to open ?
I am wanting to be able to add as many different instances of data, while the user has not stated 'n', but then it only ever writes back to the screen the input for the last set of data. Where as I want to display back to the screen all the data that has been entered.
It has something to do with the lines at the bottom of the code. It doesnt cout anything. The program just crashes upon execution. First, it asks me the amount of students i want to handle. I enter '1'. Then it asks me if i want to read in from external file and i enter 'Y'. then the exe just crashes
Name: Mary Smith Exam 1: 65 Exam 2: 79.1234 Exam 3: 70.24
Becomes something like this in the output file:
Name: Parker, Peter Average Score: 92.28 Grade: A
Name: Smith, Mary Average Score: 71.45 Grade: C
I know I'm supposed to read the whole file, but I'm getting really confused on how to take the name of each student separately without recording Exam 1, 2, and 3. I'll be able to do the average score and grade on my own.
Is there a way to indicate how many records exist in a given file? For example, vectors have the vector.size() command to show the number of given elements. Is there a such command for files and records?
The directions are to write a program that reads sorted integers from two separate files and merge the contents of the file to an output file (third file). The only standard output will be any errors to be reported and a “FINISHED” statement after all items have been processed.
file1.txt 2 4 6 8 10
file2.txt 1 5 11 12 15
Output.txt 1 2 4 5 6 8 10 11 12 15
This is the code I have so far, but it is not working, and I have put the two txt files in the same directory as my .cpp file. It is not working though still. What have I done wrong and how can I fix it to read these integers from the two numbers and merge the contents into a third file?
#include <iostream> #include <fstream> using namespace std; int main() { int num1; int num2; ifstream inputFile;
I'm messing around with reading and writing files. The first file creates a small txt file. Simple enough
#include <iostream> #include <fstream> #include <string> using namespace std; int main(){ string name; string desc;
[Code] ....
It does what it should. It creates a text file "items.txt" .... It reads as such:
dagger,a dagger,15,10,0,1,3,1,0,0,0,1,0,0,0,0,0,1
The second file is meant to read the file and place the data back into the variables. This happens, but the data crams itself into the first variable, and the rest of them collect the trash that's in memory.
#include <iostream> #include <fstream> #include <string> using namespace std; int main() { string name,desc;
[Code ....
I need to get "dagger" into name, "a dagger" into description, and each value with their perspective variable. I'm sure I need some type of "separator". Hopefully I can use the comma. Before it's over, I will have about a hundred items that will need to be read into a class of items.
My assignment was to take numbers from two different files, and merge them into a third file in numerical order. I have everything working well, but the output shows the lowest number everytime and i'm not sure why. logical error ....
struct magic { char windowsheader[2]; } magicnumbers; struct bmp { unsigned int sizeofthefile; short int applicationspecific1;
[Code] .....
When I run this program, seems like it is working,at least I am sure that it gives the right file size. But if I don't use struct magic and instead use:
Code: struct bmp { char windowsheader[2]; unsigned int sizeofthefile; short int applicationspecific1; short int applicationspecific2; //same lines with above } bitmap_header;
And if I don't use first fread:
Code:
fread(&magicnumbers,sizeof(magicnumbers),1,fp);
Then the values which structure "bmp"'s variables get become wrong. Of course I change the related printf to:
... so a very simple file format. and what i need to do is to read that into memory (vector of strings) so that header info and seq info is in two different vectors. for that i am using the following function :
this code does what is suppose to do but it is EXTREMELY slow. it takes me exponentially more time to read the seq in memory then to process it. when compared to c style alternative that reads character by character it takes 13 sec with this function to do the same job that my c function does in 0.03 sec. How to improve upon this function to make it comparably fast (also i am using optimization) ?
I want my program to be able to read text files in the format:
number number number number number number...
and so on, so there are two columns of values. The problem I'm having is, there are a lot of numbers in the file, and it can vary. The program needs to read the numbers, put one column into one array, and the other in another, perform some operations on it all, and eventually pop out two different arrays. In other words, after I've got these arrays, I don't need them for much longer. I was hoping I could dynamically allocated some arrays to store the numbers and just free them as soon as I'm done with them.
If the file wasn't of such variable size or if it was guaranteed to be under a certain number of variables, I would have used:
program that I am working on. I want to use fgets() in my program so I could handle multiple words from a text(to be able to handle spaces). I get a weird result when running the program.
