Read limit byte with C language

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1.00/5 (1 vote)

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hey everyone
i have a image , i want when i start to read the image by the file in c programming , read by block or a limit number of byte defined before , it means read a limit byte for example 32 byte , after i want to calculate the probability for every byte in this block
thankx

What I have tried:

FILE *fp=fopen("image.pgm","rb")
while (c=fgetc(fp)!=EOF)
{
//read the 32 first byte
//calcule the probability of every byte
//return to position 32 in the file
}

Posted 26-Aug-16 23:11pm

yagami_md

Updated 20-Oct-16 3:31am

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3 solutions

Solution 1

You have done nothing and we don't do your homework.

You better learn C properly, and follow tutos:

The C Programming Language - Wikipedia, the free encyclopedia[^]
https://hassanolity.files.wordpress.com/2013/11/the_c_programming_language_2.pdf[^]
http://www.ime.usp.br/~pf/Kernighan-Ritchie/C-Programming-Ebook.pdf[^]

Posted 26-Aug-16 23:19pm

Patrice T

Updated 26-Aug-16 23:36pm

v2

Comments

yagami_md 27-Aug-16 5:30am

thank you , every one have a level question it means learn !

Patrice T 27-Aug-16 5:40am

the 2 last links are the reference book by the authors of C Language.
Take time to read it, it is worth the cost.

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Richard MacCutchan · Accepted Answer · 2016-08-26T23:46:00

Solution 2

Do not use fgetc to read files, especially binary data. Use fread as described at https://msdn.microsoft.com/en-us/library/kt0etdcs.aspx[^].

Posted 26-Aug-16 23:46pm

Richard MacCutchan

Comments

yagami_md 20-Oct-16 7:49am

hi friend ...im stopped my work since 2 month ..i want to end that ..please can you give me how read image by block? for example in FILE stream i would like read 64 byte by byte !!! thank you

Richard MacCutchan 20-Oct-16 8:00am

Follow the link I gave you, it shows exactly how to do it.

yagami_md 20-Oct-16 8:03am

please friend im a bgenner in c language i want help
that what i want do
FILE *stream ;

FILE *stream1;

stream= fopen(pFile, "rb");

//when stream still bytes in stream

do

{

numread = fread( stream1, sizeof( char ), 64, stream );

//treat the stream1

}

Richard MacCutchan 20-Oct-16 8:10am

I have given you help - go and read the information on that link. There is no point in me repeating what is already provided.

yagami_md 20-Oct-16 8:24am

i copy all the whole file to buffer ... how i can read from the buffer?

Richard MacCutchan 20-Oct-16 9:15am

Use a pointer or index to access each byte. This is basic C language, if you do not understand the basics then go back to your study guides, or try some of the many online tutorials.

Richard MacCutchan · Accepted Answer · 2016-10-20T03:31:00

This is the very basic code to read the file

C++

unsigned char buffer[64];	// buffer may be any size
FILE *fp = fopen("image.pgm", "rb");
int numread;

while (!feof(fp))  // repeat until reached end of file
{
    int index;	// index into the buffer
    numread = fread(buffer, sizeof(unsigned char), 64, fp);
    if (numread == 0)
        break;  // no data left to read
    for (index = 0; index < numread; ++index)
    {
        // process each byte of the buffer
        int b = buffer[index];	// b contains the value of the current byte
        printf("byte %d: %d\n", index, b);
    }
}