Real time display of .jpeg in byte array using C - c

Question

I am working on a project where I have a server that sends an encrypted jpeg to a client which then decrypts it. Currently the image is stored in a byte array on the receiver end before it is written to the current directory.
void decryptionFunction(){
uint8 *plaintext; /* Pointer to buffer that contains decrypted jpeg
data*/
uint32 plaintext_len;
int k = 0;
while(1){
/*Decryption happens here... malloc() buffer and set *plaintext
equal to it*/
char buffer[32];
snprintf(buffer, sizeof(char) *32 "file%i.jpeg", k);
FILE *fp;
fp = fopen(buffer, "wb");
fwrite(plaintext, 1, plaintext_len, fp);
fclose(fp);
k++;
free(plaintext);
}
}
Each time the while loop completes a new image is placed in the buffer and then writes the image to the current directory. This all works fine, however I would like to display the image somehow instead of writing it to the current directory. Is there a way to do this in C? I have currently thought about streaming it from the receiver to VLC using some protocol, but that seems a little more complicated than what I am wanting.
Ideally, I would like to just display the image from the buffer and refresh the display each time through the while loop.
Thanks for any input.

Answer 1

There are many different libraries to display an image. One lite/simple is NxV. You can also use QT.

Answer 2

I found a solution that will work for right now. I decided to use the OpenCV library which has deprecated C functions to handle image display.
void decryptionFunction(){
uint8 *plaintext; /* Pointer to buffer that contains decrypted jpeg
data*/
uint32 plaintext_len;
int k = 0;
while(1){
/*Decryption happens here... malloc() buffer and set *plaintext
equal to it*/
CvMat matbox = cvMat(240, 320, CV_8UC1, plaintext);
IplImage *img;
img = cvDecodeImage(&matbox, 1);
cvNamedWindow("test", CV_WINDOW_AUTOSIZE);
cvShowImage("test", img);
cvWaitKey(100);
cvReleaseImage(&img);
free(plaintext);
}
}
While these functions are deprecated and can be cut at any time, for the time being they do exactly what I want. The buffer contains compressed jpeg data, and in order for it to be shown in the window, it has to be decoded into a raw format. I am still looking for a C implementation that can do exactly this that isn't deprecated.

Answer 3

You can maybe use the display program which is part of the ImageMagick suite which is installed on most Linux distros and is also available for OSX and Windows.
Basically, at the command line, you do:
display image.png
and it shows the image. It can display PNG, JPEG, TIFF and around 150 other formats. If your image changes, or you want to display a different one, you can do the following and it will look up the first instance of display and tell it to refresh with the new image:
display -remote image2.jpg
It can also take the image from its stdin as long as you tell it what type of file is coming, so it will work just as well like this:
cat image.jpg | display jpg:-
So you could effectively use popen() to start display and then send your image buffer to its stdin and then, when your image changes, run it again with the added -remote parameter to make it look up the first displayed image and refresh it rather than opening another display.
There are many options to resize the image before display, overlay it on a solid background or texture and so on if you run man display.