can't read bmp file perfectly - c

I am newbie in C ,I write a c code for simply reading a bmp file of 2448x280 pixels having 32 bit depth and writing it into new bmp file. For this I read pixels one by one. I am reading header perfectly , but the problem is after completing read and write operation on pixels, the current position original image is= 2741814, which is right according to me but result image is have its position = 2903490. So, please tell me where is the mistake.
Here is my code:-
#include<stdio.h>
#include<conio.h>
void main(void)
{
long int length;
int count,r,c,p;
FILE *image;
FILE *result;
char read_pixels;
image=fopen("image.bmp","rb");
result=fopen("result.bmp","w+");
for(count=0;count<54;count++)
{
fread(&read_pixels,1,sizeof(read_pixels),image);
fprintf(result,"%c",read_pixels);
}
for(c=0;c<280;c++)
{
for(r=0;r<2448;r++)
{
for(p=0;p<4;p++)
{
fread(&read_pixels,1,sizeof(read_pixels),image);
fprintf(result,"%c",read_pixels);
}
}
}
fseek(image,0,SEEK_CUR);
length=ftell(image);
printf("position of image after reading pixels =%d\n",length);
fseek(result,0,SEEK_CUR);
length=ftell(result);
printf("position of result after writing pixels=%d\n",length);
fclose(image);
fclose(result);
getch();
}

Related

Mirror image read from 2D array in C

I am writting a program in C in which i'm reading a bmp image with a 2D array. I am supposed to have as output the original image + its inverse right next to each other.
The code I have here should be doing that but the images print on top of each other. I appreciate the help if anyone knows how I can fix that.
int main(void) {
// Opens file to read the image from
FILE * infile = fopen("inputImage.bmp", "rb");
// Creates file to write the image to after modifications
FILE * outfile = fopen("flip.bmp", "wb");
//Bmp images have headers the next 3 lines of code store the header of the input image
unsigned char headersPart1[2];
int filesize;
unsigned char headersPart2[48];
// This space[] [] creates the array to which to write the input image AND its inverse right next to each other the image file is 160 * 240
// The 3 is for the rgb values.. since its a 2D array we want to use every single //part of the image to work with
unsigned char space[160][3*240];
//The array to which to copy the results to (original image + INVERSE)
unsigned char mirror[160][3*480];
fread(headersPart1,sizeof(char) ,2,infile);
fread(&filesize,sizeof(char) ,4,infile);
fread(headersPart2,sizeof(char) ,48,infile);
fread(space,sizeof(char) ,filesize-54,infile);
// copying what in the original image array (space[][]) into the new //array mirror[][]
for ( int row = 0; row < 240*3 ; row++ ) {
for (int col = 0 ; col < 160; col++) {
char temp = space[col][row];
mirror[col][row] = space[col][row];
//Starts printing the inverse of the original image, starting at the index where the original image will end
mirror[col][720+row]= space[col][719-row];
space[col][row] = temp;
}
}
// Puts everything back into the outfile , once i save and run on GCC this gives me an image and its inverse on top of each other
fwrite(headersPart1,sizeof(char) ,2,outfile);
fwrite(&filesize,sizeof(char) ,4,outfile);
fwrite(headersPart2,sizeof(char) ,48,outfile);
//sends whats in mirror [][] to the outfile
//54 is the size of the header (bmp images))
fwrite(mirror,sizeof(char) ,filesize-54,outfile);
return 0;
}
PS: I'm running this on GCC
The BMP file format you can find here
Your loader is not complete regarding support different versions of BMP, check resolution, color-depth, the presens of palette etc.
But for what you want to use this for, you probably have a fixed input, always the same resolution etc.
But you want the resulting image to be twice as wide. Hence some details in the headers has to change:
"filesize"
"the bitmap width in pixels (signed integer)"

Searching a particular string in a large file

I am making program in C which can search for a specific string in a large .txt file and count it and then print it out. But it seems that something have go wrong, cause the output of my program is different from that of the two text editor. According to the text editor, there are totally 3000 words,in this case I search for the word "make", in that .txt file. But the output of my program is just 2970.
I cannot find out the problem of my program. So I am curios about how could a text editor search for a specific string so accurately? How do people implement that? Can any people show me some code in C?
To make things clear: that is a large .txt file, 20M or so, containing lots of characters. So I think it's not so good to read it into memory all at once. I have implement my program by splitting my program in to pieces and then scan all of those for parsing. However, it fail some way.
Maybe I should put the code here. Wait a minute please.
The code is kinda long, 70 lines or so. I have put it on my github, if you have any interest, please help. https://github.com/walkerlala/searchText
note that the only related file is wordCount.c and testfile.txt which goes like:
#include<stdio.h>
#include<stdlib.h>
#include<stdbool.h>
char arr[51];
int flag=0;
int flag2=0;
int flag3=0;
int flag4=0;
int pieceCount(FILE*);
int main()
{
//the file in which I want to search the word is testfile.txt
//I have formatted the file so that it contain no newlins any more
FILE* fs=fopen("testfile.txt","r");
int n=pieceCount(fs);
printf("%d\n",n);
rewind(fs); //refresh the file...
static bool endOfPiece1=false,endOfPiece2=false,endOfPiece3=false;
bool begOfPiece1,begOfPiece2,begOfPiece3;
for(int start=0;start<n;++start){
fgets(arr,sizeof(arr),fs);
for(int i=0;i<=46;++i){
if((arr[i]=='M'||arr[i]=='m')&&(arr[i+1]=='A'||arr[i+1]=='a')&&(arr[i+2]=='K'||arr[i+2]=='k')&&(arr[i+3]=='E'||arr[i+3]=='e')){
flag+=1;
//continue;
}
}
//check the border
begOfPiece1=((arr[1]=='e'||arr[1]=='E'));
if(begOfPiece1==true&&endOfPiece1==true)
flag2+=1;
endOfPiece1=((arr[47]=='m'||arr[47]=='M')&&(arr[48]=='a'||arr[48]=='A')&&(arr[49]=='k'||arr[49]=='K'));
begOfPiece2=((arr[1]=='k'||arr[1]=='K')&&(arr[2]=='e'||arr[2]=='E'));
if(begOfPiece2==true&&endOfPiece2==true)
flag3+=1;
endOfPiece2=((arr[48]=='m'||arr[48]=='M')&&(arr[49]=='a'||arr[49]=='A'));
begOfPiece3=((arr[1]=='a'||arr[1]=='A')&&(arr[2]=='k'||arr[2]=='K')&&(arr[3]=='e'||arr[3]=='E'));
if(begOfPiece3==true&&endOfPiece3==true)
flag4+=1;
endOfPiece3=(arr[49]=='m'||arr[49]=='M');
}
printf("%d\n%d\n%d\n%d\n",flag,flag2,flag3,flag4);
getchar();
return 0;
}
//the function counts how many pieces have I split the file into
int pieceCount(FILE* file){
static int count=0;
char arr2[51]={'\0'};
while(fgets(arr2,sizeof(arr),file)){
count+=1;
continue;
}
return count;
}
You can do this quite simply just by having a rolling buffer. You don't need to break the file into sections.
#include <stdio.h>
#include <string.h>
int main(void) {
char buff [4]; // word buffer
int count = 0; // occurrences
FILE* fs=fopen("test.txt","r"); // open the file
if (fs != NULL) { // if the file opened
if (4 == fread(buff, 1, 4, fs)) { // fill the buffer
do { // if it worked
if (strnicmp(buff, "make", 4) == 0) // check for target word
count++; // tally
memmove(buff, buff+1, 3); // shift the buffer down
} while (1 == fread(buff+3, 1, 1, fs)); // fill the last position
} // end of file
fclose(fs); // close the file
}
printf("%d\n", count); // report the result
return 0;
}
For simplicity I stopped short of making the search word "softer" and allocating the correct buffer and various sizes, since that wasn't in the question. And I have to leave something for OP to do.

My function is copying a PGM image file to PPM in a different way

I have a very simple function that saves a PPM image:
void WriteCImage(CImage *cimg, char *filename)
{
FILE *fp;
int i,n;
fp = fopen(filename,"w");
fprintf(fp,"P6\n");
fprintf(fp,"%d %d\n",cimg->C[0]->ncols,cimg->C[0]->nrows);
fprintf(fp,"255\n");
n = cimg->C[0]->ncols*cimg->C[0]->nrows;
for (i=0; i < n; i++)
{
fputc(cimg->C[0]->val[i],fp);
fputc(cimg->C[1]->val[i],fp);
fputc(cimg->C[2]->val[i],fp);
}
fclose(fp);
}
as you can see, this function receives a matrix (in CImage format) and writes the image data in the ASCII file. It seems correct, but every time I copy a grayscale image to a PPM image I have problems. Look at the code:
//that's a PGM grayscale image
gt = ReadImage(argv[1]);
//creating an RGB image with same dimensions of the PGM image
nwcimg = CreateCImage(gt->nrows,gt->ncols);
n=gt->nrows*gt->ncols;
//iterate through the PGM image
for(index=0;index<n;index++)
{
// just a copy of the grayscale image value to all 3 layeres
//of the PPM (RGB) image
nwcimg->C[0]->val[index]=gt->val[index];
nwcimg->C[1]->val[index]=gt->val[index];
nwcimg->C[2]->val[index]=gt->val[index];
}
WriteCImage(nwcimg,"gt-copied.ppm");
DestroyCImage(&nwcimg);
DestroyImage(&gt);
what problem i have? well, the code seems correct and simple. But when the cimage matrix/vector is written as a file, i can see that the two pictures are not the same. Seems like the pixels of the PGM image are 'shifted' or 'mirrored' in the copied image.
You can see the Image File and The RGB copy
Shouldn't
for(index=0;index<n;index++) {
nwcimg->C[0]->val[index]=gt->val[index];
nwcimg->C[1]->val[index]=gt->val[index];
nwcimg->C[2]->val[index]=gt->val[index];
be
for(index=0;index<n;index) {
nwcimg->C[0]->val[index]=gt->val[index++];
nwcimg->C[1]->val[index]=gt->val[index++];
nwcimg->C[2]->val[index]=gt->val[index++];
? The for loop in your file writer writes 3 bytes per loop. The loop in your reader consumes only 1 byte per loop then copies it into three separate arrays.

bitmap image file manipulation using bitmap file structure in c

I want to implement a simple command line based image editor. The program will
provide a text based menu, which provides several functions for user to manipulate a windows
bitmap (.bmp) image file. The menu will include load image, rotate image, mirror image, save image
and quit options. The load image option will be used to open and read pixel values from a given
bitmap file. This option will also print out the basic properties, such as dimensions and total size, of the given file. The rotate and mirror options will manipulate previously read pixel values. An image
must be loaded before applying these options. The save option will save the pixel values in the
memory to a bitmap file with a given filename.
Which approach do you recommend for me about this project and about bitmap file structure?
It would be very appreciated if you give me advice even about one particular topic for example load the file.
libbmp will make your program all but trivial to implement.
If you really want to use C then try the libbmp library http://code.google.com/p/libbmp/
However, I'd recommend using C#, then the task would be trivial with the System.Drawing namespace.
This function is used for loading a bmp file to memory.
you have to declare first a header file with bmp structure
BMP* load_BMP(char *filename);
BMP *bmp; // local integer for file loaded
FILE *in; // pointer for file opening
int rowsize;
int row, col, color, i;
unsigned char b;
in=fopen(filename,"rb"); // open binary file
if (in==NULL)
{
printf("Problem in opening file %s.\n",filename);
return NULL;
}
bmp=(BMP*) malloc(sizeof(BMP)); //memory allocation
if (bmp==NULL)
{
printf("Not enough memory to load the image.\n");
return NULL;
}
fread(bmp->BM,2,1,in);
if (bmp->BM[0]!='B' || bmp->BM[1]!='M')
{
printf("Bad BMP image file.\n");
free(bmp);
return NULL;
}
fread(&bmp->fileSize,4,1,in);
fread(&bmp->Reserved1,2,1,in);
fread(&bmp->Reserved2,2,1,in);
fread(&bmp->imageOffset,4,1,in);
fread(&bmp->imageHeaderSize,4,1,in);
fread(&bmp->imageWidth,4,1,in);
rowsize=4*((3*bmp->imageWidth+3)/4); //calculate rowsize because of padding
fread(&bmp->imageHeight,4,1,in);
fread(&bmp->colorPlanes,2,1,in);
fread(&bmp->compressionMethod,4,1,in);
fread(&bmp->imageSize,4,1,in);
fread(&bmp->hPPM,4,1,in);
fread(&bmp->vPPM,4,1,in);
fread(&bmp->paletteColors,4,1,in);
fread(&bmp->paletteImportantColors,4,1,in);
bmp->data=(unsigned char*) malloc(bmp->imageSize); //allocate memory for image data array
if (bmp->data==NULL)
{
printf("There is not enough memory to load the image\n");
free(bmp);
return NULL;
}
for(row=0;row<bmp->imageHeight;row++) //read picture data
{
for(col=0;col<bmp->imageWidth;col++)
for(color=0;color<=2;color++)
fread(&bmp->data[row*rowsize+3*col+color],
sizeof(unsigned char),1,in);
//read extra bytes for end of row padding
for(i=0;i<rowsize-3*bmp->imageWidth;i++)
fread(&b,1,1,in);
}
fclose(in);
return bmp;
}

creating a bitmap image from existing bitmap, in C

I am writing a C program, which will retrieve the information (header information, pixel information) from a bitmap image, and use that information to create another bitmap image (the new image will obviously be same as the original).
The problem is that, in some cases, extra bytes get added (on their own) to the new image, due to which the image is not formed properly.
In another case, some bytes get missing in the new image, due to which image formation itself fails.
(This happens while writing the pixel information. the bitmap header information gets written properly to the new file.)
I have debugged the code but I couldn't find out what is causing this.
I'll be glad if somebody could tell me what the error is.
//creating a bitmap file
#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<math.h>
long extract(FILE *,long ,int );
long extract(FILE *fp1,long offset,int size)
{
unsigned char *ptr;
unsigned char temp='0';
long value=0L;
int i;
//to initialize the ptr
ptr=&temp;
//sets the file pointer at specific position i.e. after the offset
fseek(fp1,offset,SEEK_SET);
//now fgetcing (size) values starting from the offset
for(i=1;i<=size;i++)
{
fread(ptr,sizeof(char),1,fp1);
value=(long)(value+(*ptr)*(pow(256,(i-1)))); //combining the values one after another in a single variable
}
return value;
}
int main()
{
int row,col;
int i,j,k;
int dataoffset,offset;
char magicnum[2];
FILE *fp1,*fp4;
clrscr();
if((fp1=fopen("stripes.bmp","rb"))==NULL)
{
printf("\a\nCant open the image.\nSystem is exiting.");
exit(0);
}
if((fp4=fopen("op.bmp","a"))==NULL)
{
printf("\n\aError while creating a file.\nSystem is exiting ..... ");
exit(0);
}
fputc((int)extract(fp1,0L,1),fp4);
fputc((int)extract(fp1,1L,1),fp4);
fputc((int)extract(fp1,2L,1),fp4);
fputc((int)extract(fp1,3L,1),fp4);
fputc((int)extract(fp1,4L,1),fp4);
fputc((int)extract(fp1,5L,1),fp4);
fputc((int)extract(fp1,6L,1),fp4);
fputc((int)extract(fp1,7L,1),fp4);
fputc((int)extract(fp1,8L,1),fp4);
fputc((int)extract(fp1,9L,1),fp4);
fputc((int)extract(fp1,10L,1),fp4);
fputc((int)extract(fp1,11L,1),fp4);
fputc((int)extract(fp1,12L,1),fp4);
fputc((int)extract(fp1,13L,1),fp4);
fputc((int)extract(fp1,14L,1),fp4);
fputc((int)extract(fp1,15L,1),fp4);
fputc((int)extract(fp1,16L,1),fp4);
fputc((int)extract(fp1,17L,1),fp4);
fputc((int)extract(fp1,18L,1),fp4);
fputc((int)extract(fp1,19L,1),fp4);
fputc((int)extract(fp1,20L,1),fp4);
fputc((int)extract(fp1,21L,1),fp4);
fputc((int)extract(fp1,22L,1),fp4);
fputc((int)extract(fp1,23L,1),fp4);
fputc((int)extract(fp1,24L,1),fp4);
fputc((int)extract(fp1,25L,1),fp4);
fputc((int)extract(fp1,26L,1),fp4);
fputc((int)extract(fp1,27L,1),fp4);
fputc((int)extract(fp1,28L,1),fp4);
fputc((int)extract(fp1,29L,1),fp4);
fputc((int)extract(fp1,30L,1),fp4);
fputc((int)extract(fp1,31L,1),fp4);
fputc((int)extract(fp1,32L,1),fp4);
fputc((int)extract(fp1,33L,1),fp4);
fputc((int)extract(fp1,34L,1),fp4);
fputc((int)extract(fp1,35L,1),fp4);
fputc((int)extract(fp1,36L,1),fp4);
fputc((int)extract(fp1,37L,1),fp4);
fputc((int)extract(fp1,38L,1),fp4);
fputc((int)extract(fp1,39L,1),fp4);
fputc((int)extract(fp1,40L,1),fp4);
fputc((int)extract(fp1,41L,1),fp4);
fputc((int)extract(fp1,42L,1),fp4);
fputc((int)extract(fp1,43L,1),fp4);
fputc((int)extract(fp1,44L,1),fp4);
fputc((int)extract(fp1,45L,1),fp4);
fputc((int)extract(fp1,46L,1),fp4);
fputc((int)extract(fp1,47L,1),fp4);
fputc((int)extract(fp1,48L,1),fp4);
fputc((int)extract(fp1,49L,1),fp4);
fputc((int)extract(fp1,50L,1),fp4);
fputc((int)extract(fp1,51L,1),fp4);
fputc((int)extract(fp1,52L,1),fp4);
fputc((int)extract(fp1,53L,1),fp4);
//setting the file pointer at the beginning
rewind(fp1);
/*CHECKING WHETHER THE FILE IS IN BMP FORMAT OR NOT, WE CHECK THE MAGIC NUMBER OF THE FILE, MAGIC NUMBER'S OFFSET IS 0 i.e. IT'S STORED AT THE FRONT OF THE IMAGE, AND THE SIZE IS 2*/
//at first extracting the magic number
for(i=0;i<2;i++)
{
magicnum[i]=(char)extract(fp1,i,1);
}
//now checking
if((magicnum[0]=='B') && (magicnum[1]=='M'))
;
else
{
printf("\aThe image is not a bitmap image.\nSystem is exiting ... ");
exit(0);
}
//storing the header information
//get the starting position or offset of the data(pixel)
dataoffset=(int)extract(fp1,10,4);
//get the number of rows
row=(int)extract(fp1,22,4);
//get the number of columns
col=(int)extract(fp1,18,4);
//storing the data
offset=dataoffset;
for(j=0;j<col;j++)
{
for(k=0;k<row;k++)
{
for(i=0;i<=2;i++)
{
fputc((int)extract(fp1,offset++,1),fp4);
}
}
}
fcloseall();
return 0;
}
Make sure you open the output file in binary mode as well.
If you don't do that, the byte value corresponding to '\n' may be expanded to carriage return and line feed.
Consider this line:
value=(long)(value+(*ptr)*(pow(256,(i-1))));
pow is a floating point function returning a double. This means that (*ptr) is implicitly casted to double. The whole expression (value+(*ptr)*(pow(256,(i-1)))) will be a double. Now this can be larger than 2147483647 which is the largest number a long can hold (on most common 32-bit platforms), and the result when converting an out of range double to long is undefined. See what happens on this example:
#include <stdio.h>
int main(int argc, char **argv) {
int i;
for (i = 0; i < 10; i++) {
double d = 2147483647.0d + i;
printf("double=%f long=%ld\n", d, (long)d);
}
return 0;
}
Here is the output when I run it on my system: (hidden in case you want to guess or test it yourself first):
double=2147483647.000000 long=2147483647
double=2147483648.000000 long=-2147483648
double=2147483649.000000 long=-2147483648
double=2147483650.000000 long=-2147483648
double=2147483651.000000 long=-2147483648
double=2147483652.000000 long=-2147483648
double=2147483653.000000 long=-2147483648
double=2147483654.000000 long=-2147483648
double=2147483655.000000 long=-2147483648
double=2147483656.000000 long=-2147483648
One way to fix it would be to change it to unsigned long instead.
Personally I'd use 1 << (8*(i-1)) instead of pow to avoid messing with floating point, but there is lots of other things that I'd do very different too, but that is probably out of scope for this question (might be a question for the code review site).

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