C++ :: JPEGs Recovery From Forensic Image - Optimizing Code
Jan 21, 2013
I'm taking a CS course and we've been tasked with creating a program that recovers jpegs from a formatted CF card which uses the FAT file system with a block size of 512 bytes, the jpegs in the card are block aligned which means that the beginning of a jpeg marks the end of the former.
I've wrote the program and it works nicely and recovers the 51 jpegs in the CF card (actually just an image of some 4-5 megabytes of the actual card which can be downloaded here) but I'm looking for ways to optimize/improve my code so I need a second look from experienced programmers.
Here's my code:
Code:
/*
* filename : recover.c
* description : Recovers jpegs from a forensic image
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#define BLOCK 512 // fat file system block size
int main(void) {
// open CF card image
[Code] .....
My questions are:
1) What are the possible optimizations that can make my code faster/better/more concise?
2) I'm not handling slack space, since trailing zeros at the end of a jpeg won't affect rendering it (we were told it won't contain any garbage values)... how may I approach the problem?
3) Can I enhance my if else constructs? or even replace them with something more elegant?
I have written a tar program and now I can take files add them to a tarfile and extact them into another directory. The problem is that it doesn't work with jpegs. I imagine in it has to do with how I am reading and writing because it is a binary file. I have used "rb" "wb+" etc for accessing the files.
i am looking for a verified code in simple c, for generating fft of an input image (.jpg). the output can be a text file including fft coefficients.can you recommend me any source except open-cv?
I've written a timer function in c/c++, but it still has performance problems. how to optimize this further (atm works with delay to perform timing):
#include "headers/types.h" //Basic types! #include "headers/timers.h" //Timer support function data! #include "headers/emu/threads.h" //Thread for timer item! //Timer step in ms! Originally 100ms #define TIMER_STEP 10000
Today I came across a problem that I've never had before and haven't thought about. Until now, The optimizing and speed in a program. I've created a small and very easy user input based "Word Generator" just to test and compare other programs.
I have compared my program to another program that works on the same concept that is programmed in C#. What I've heard is that C++ is one of the fastest languages, but still. The C# program I compared to was about 15 seconds faster when both generating 100 000 words.
optimize this program down below and describe what you've done.
btnStatusPlr1.Image SHOULD come back as True.Then I realized it might not be the same as setting the buttons image in the properties (Which is what i did to get the original image (the one being compared to))
I do have a feeling ive done something wrong here (Yes im a noob /> )
Variable active, is the same image as the buttons default (Well should be)
I have a class 'A' which is almost perfect for my needs. Class 'B' uses class 'A' I've now designed Class 'C' and Class 'D' and noticed that there is a good chunk of code in class 'B', 'C' and 'D' for using Class 'A' is duplicated. I've separated out this code in specific, standalone functions in each of the classes. Now I'm wondering where this code should go. At the moment, the functions are duplicated in the three calling classes (B, C and D). Placing the functions into class 'A' would break the single responsibility principle. Inheritance to add functionality would likely break both SRP and LSP. The one that seems that it may work is composition.
However, Is designing a complete class just for a few functions over kill?
Would it be valid for classes 'B', 'C' and 'D' to access both the new class 'E' (which would depend on A) and the old class 'A' (which would have to be the same instance as the instance in the new class 'E'), or should the new class 'E' provide sufficient functionality so that Classes B, C and D don't need to access Class A directly? It would seem that its then an incomplete interface of the original object with additional functionality (ie, incompatible) Or should I do it a completely different way?
I am working on pset4 in the CS50 online coarse. The goal is to resize a bmp image. I have it working except adding the padding back to new resized image. The image I am using uses 3 bites of padding. If the factor I resize the image by works out to have 3 bites of padding it works perfect and if the image has no padding it works perfectly I need a fresh pair of eyes. I am not sure how to add the images so here is the address to download the images and the skelton of the source code they gave to modify. [URL] .... The image that requires the padding is labled as small.bmp.
#include <stdio.h> #include <stdlib.h> #include "bmp.h" int main(int argc, char* argv[]) { // ensure proper usage if (argc != 4)
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// includes #include <windows.h> #include <stdio.h> #include "res.h"
The problem i have faced is image is getting cropped.
I want to rotate an image without cropping. I have searched a lot but I am not getting any algorithm based on C. How to get the algorithm for image rotation without cropping.
I'm trying to edit an image by multiplying the red component of each pixel by 10 and leaving the other components (green and blue) untouched. I'm not really sure how I'm supposed to edit the pixels one by one. I have this so far. I think there is something wrong with my ppm header as well. Is there a way to make a ppm header without specifying the bounds so that it conforms to the image you are putting in?
I am trying to read a 24 bit image but I'm getting errors when I'm tryting to read the pixels.
-The reading part looks bad because I'm reading both headers field by field. But I'm sure that it is reading both headers correctly.
-Right now my biggest concern is to get it to read successfully an entire bmp image
I'm using this calculation to get my padding bytes:
padding bytes = [4-(3*width)mod 4]mod 4
When I use a 2x2.bmp file to test it, I get an error that the [1][1] pixel was not read. When I use a bigger image it gives me the same error after about 100 rows and then every pixel is an error from that point on. This is what I got so far:
I'm supposed to print a small rectangle inside concentric circles that are inscribed in a rectangle.I'm not really sure where to start with printing a circle in a ppm file.
I'm pretty new to C, just looking to see how to display a image and some text to go along with it so far I can display in the image but cannot display the text at the same time.
how to do the mirror function? I have my other two working 100% but for some reason i cannot figure out how to do the mirror part. I want it to be like my flip function(lower code) where I can print the image through the for statement
Code:
int main (int argc, char *argv[]) { // declarations here // open input file FILE *input;
I have an assignment where I need to take an assigned image, rotate it 90 degrees to the right, flip it upside down, and turn it to grayscale; each with different outputs.
I was thinking if I can read in the image into a 2d array //array[height][width] or even just an array with the values of each pixel (r, g, b), I can just modify the array and spit it out when done.
if i can just get it into the array, I think I'll be fine. We've done similar assignments with modifying arrays for grayscale images and the other two I can probably figure out. But how am I going to read in each pixel into an array with three different values in each slot? This is my code so far:
I am trying to re-size a bitmap image for a class.They gave us two options to use to do the program with: an array or move the file position indicator. I want to use the file option. All the bitmap header info is checking out. The file after being re-sized should be 822 bytes but it is 1.6 KiB and the image is distorted.
Code:
#include <stdint.h> /** * Common Data Types * * The data types in this section are essentially aliases for C/C++ * primitive data types.
This is my first time using opengl and I am experimenting with adding/drawing polygons/points/etc. on top of a PPM image. The image is already loaded when the application runs. My attempt to draw a square is from lines 30 - 35. The program runs but the square is not present. Just the image.
My assignment is use a 3D array to create an image. Use an array of the form arr[300][200][3]. For this homework, you need to use an array of the form arr[3][400][500]. It will have 400 rows and 500 columns. You need to first initialize the array as described in class and after that write the array to a ppm image file. When viewed using Gimp, it should display USM. The letters would be 200 pixels high and 100 pixels wide each. Use at least 15 pixels for the width of the stroke. Use different colors for each letter and a different color for the background.This is what I have so far.
#include <iostream> #include <fstream> #include <string> using namespace std;
void initialize(unsigned char a[][200][3], int nrows, int ncols, int nc); void printAll(unsigned char a[][200][3], int nrows, int ncols, int nc);
