C++ :: Reading JPEG Pixel And Change It After Comparing
Feb 28, 2014
I'm trying to read a jpeg pixel and then compare it if it'x bigger than a number to change it. Either I'm breaking the folder if I start less than 22000 which is very large number shouldn't include the header or I'm getting solid color without any different.
I need to save RGB values of each pixel in a 3D array A[width][height][3]. I found a code online that transfers the bytes into an array but I cant understand how bytes are saved them so i could transfer them into an array. The truth is I dont know much about working with images at all so i have a problem working on them. How to transfer the RGB data from an .jpeg image into a 3D array? This is my code so far:
#include <iostream> #include <jerror.h> #include <jpeglib.h> using namespace std; int main(){ FILE *pic = fopen( "image.jpeg", "rb+" );
I have managed to successfully extracted the BMP file header and file info but ran into troubles with getting the pixel data out into a 2d array.This is my function to read the data while i have another to write the data. The output does not match the input at all.
void BMPProgram::GetPixelData(std::ifstream & inStream) { std::cout << "Entered function"; if(inStream.fail()) return; //space allocated to reading in of padding int paddingSpace = 0;
[Code] ....
PIXEL is a struct of 3 unsigned char containing values of RGB.
Problem in converting Jpeg to DIB, Iam using the same code for Jpeg RGB(Jpeg_color_space=JCS_RGB) and Grayscale Images(JCS_GRAYSCALE). this code works correctly for Jpeg RGB Images when i create DIB for 24 bit. But for Jpeg Grayscale(JCS_GRAYSCALE) images, when i am converting to DIB I get a Black color space next to image,but the original image does'nt contain any black space.
Following is the code i use for converting jpeg to DIB.
//Function to convert jpeg to dib.
int convert_jpeg_to_dib(const char * filename) { struct jpeg_decompress_struct cinfo; unsigned char * buffer; int result = 0; struct my_error_mgr jerr; FILE * infile; /* source file */ int row_stride; /* physical row width in output buffer */
I have a JPEG in memory as a char* and a bytesize, if I save it to disk with a .jpg extension it's a perfect JPEG file. The thing is, I don't want to save it unless it's a minimum width/height. I got it into memory using a socket recv() call. What should I do ?
I was trying to capture entire web screen and save as .jpeg format.
So far I have done this using C# Windows Application.
Same thing I am willing to do in 'VC++ 2010 Win32. In my C++ project I have created a Toolbar with a button on IE 9 browser. And on Toolbar button click I can print current window.
But I don't know how to take a snapshot and save to specified directory in .jpeg format using VC++ 2010. I have Windows 7.
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.
My coin/money change code works when there can be an exact change each time, i.e. when the 1 cent option is available. However, when the change options are only $10, $5, $1, 25 cents and 10 cents, it does not give me what I want for instance, I wanted to get change for $237.80, I was expecting to get:
23 10's, one 5, two 1's and 8 dimes. However, the code below is giving me 23 10's, one 5, two 1's and 3 quarters (there is no option left for the 5 remaining cents).how to fix it?
Code: #include<iostream> #include<algorithm> #include<vector> using namespace std; void change(double cents, int a[]); int main() { double Dollars; double cents;
I am working on image processing in C + + and opencv, I treat images in grayscale, ie the pixel values it must be between 0 (black) to 255 (white).
Mat img; img = imread (file, -1); for ( int i = 0; i < img. rows ; i ++) { for ( int j = 0; j < img. cols ; j ++) { val_pixel=img.at < double >(i,j); printf( "%d ",val_pixel); } printf( " "); }
when displaying the pixel value from two loop, I get values to 0 and it is normal for propablement black areas, but for whites I find the value -2147483648. I don't understand why this value is not 255.Is there an explanation for this has value.
I have an image of size 640x480 pixels. It's possible to obtain the dimension in mm of one pixel from that image given only that size?I do not have the size of the image in mm,however.
I wrote a script that generates n random pixel positions and draws them to the screen. Works well. Now i tried to rotate them. Rotating does work too. But it does not work as i planned it.
paramters 'angle' and 'timestep' work somehow, but not as they should do. the function 'move' is supposed to rotate the pixelfield 'angle' degrees in a given direction, addicted to the 'timestep' parameter. 'timestep' is needed time for drawing in one single game loop.
rotation point is the middle of the screen. when i set angle to 10 it should rotate 10 degrees / second. Instead it's rotating very very fast and all stars are moving nearer to the center of the screen, so after x rounds there is just 1 pixel left in the middle of the screen. there is a kind of gravition.I'm working with SDL2. What I did find out:
FPS is <= 60, 'cause of the 'SDL_RENDERER_PRESENTVSYNC' flag. When i skip that flag, for any reason the 'gravition' would take more time. FPS is <= 1400 then, 'though i got a natural game loop (i hope):
Im new to c#. In c++ I have made a window and painted it with dots and concentric circles, like a radar PPI screen. Trying to do this in c#, I can't find how to draw a single pixel on the window.
Also, what should I be drawing on: the form, panel, picturebox...?
I would like to subtract one image from another to get something like "differential picture" (i am not sure whether the name is correct). I've managed to read the FILEHEADER and FILEINFOHEADER of bitmap. I will subtract 24-bit bmp files only. However i can't understand the structure of this file. So far my code looks like this. Any example of at least copying one bmp file to a new one? This example would be useful, because subtracting will be simillar, instead of copying the pixel value i will just put abs(value1-value2) in the output.
Code:
// ConsoleApplication1.cpp : Defines the entry point for the console application. #include "stdafx.h" #include <iostream> #include <fstream> using namespace std; struct BITMAPfileHEADER {
//Casting a void pointer pointing to an array of memory locations(the pixels), to a pointer to an array of Uint8's. //SDL_MapRGB() Returns an Uint32 containing the color 0,0,255,(0/255, i think it returns the transparency too, or else it would rather return a Uint24,not sure).
Then modifying the memory location, in this case the pixel at the middle of the window.
What i seem to not understand is that, i cast pixels to Uint8*, which means I now have a pointer to an array of 8bit numbers, but SDL_MapRGB seemingly returns an Uint32 or Uint24 for a color composed of r,g,b, together without 'a' is 24bits(256=1b,256=1b,256=1b)=3b.
And then i somehow assign that pixel which is of 8bit at chosen location, an Uint24 or 32bit unsigned int.
I'm currently working with linear VRAM (a buffer with 256KB memory, divided into four 64k planes, so plane 0 at 0x00000, plane 1 at 0x10000, plane 2 at 0x20000, plane 3 at 0x30000). Just add the index of the plane to that for the full address in VRAM.
I'm still wondering how to get a specific pixel from VRAM (x,y coordinate) when doing graphic modes (none color modes work, only the black/white pixels (1-bit) graphic mode works).
how I can get specific pixels from the VGA VRAM (having linear access described above) using Shift Register Interleave mode (VGA modes 4&5), 16-bit planar mode (Most VGA modes) etc.
