Hi Madhur,
Thanks for your email.
The way you have used the PNGwriter constructor seems ok to me, what
would be really useful is a backtrace from the point where the program
crashes.
Ah! Wait a second, I have just read your follow-up (the email I'm
replying to now) and I'm a bit puzzled. Indeed, your program crashes on
my machine as well (OS X 10.3).
A few things to note:
int main (int argc, char **argv) {
int i=0, j=0, k=0, col=0;
int dcol_r=0xffff/NCOL_R, dcol_g=0xffff/NCOL_G,
dcol_b=0xffff/NCOL_B;
long int pixel;
pngwriter image (w, h, 0, output_file_name);
//0.3 0.3 1 0.5 0.5 30 10 output_file_name
if (argc<9) { cout<<"USAGE: julia_xpm cr ci zoom creal cimg w
hmax_itr output_file_name\n"; return 0; }
cr=atof (argv[1]);
ci=atof (argv[2]);
zoom=atof (argv[3]);
creal=atof (argv[4]);
cimg=atof (argv[5]);
w=atoi (argv[6]);
h=atoi (argv[7]);
max_itr=atoi (argv[8]);
output_file_name=argv[9];
cout<<"Arguments read successfully\n";
You set the user-supplied values for width and height *after* the
pngwriter constructor is called. I haven't checked if you resize the
image later but it is worth noting. w and h have default values so this
shouldn't be a critical problem.
In fact, I removed all mention of PNGwriter from your code and it still
crashes. Am I correct in assuming then that this is not a
PNGwriter-related bug? If that is the case, I'm as stumped as you are,
and I'm definitely no code guru. You might want to take this issue to a
C++ list. If you do figure it out, I'd be interested in knowing what
was wrong.
Best of luck.
Paul
On 2 Aug 2005, at 19:20, Madhur Kashyap wrote:
Hi Paul,
After struggling for some more time I found the reason behind the
problem. I did not expect this to be the problem. If possible for you
please clarify the reason because I am unaware of any such thing.
While cruising the code through gdb the code used to crash as soon as
I step into the main() function. After removing every single compile
time option and extra piece of code, I found out that the error was
because of creating an array of a structure (size 3 ints) of large
number of elements. Look at the code snippet at the end of email....
MAX_COLORS=16777216 in the code.
I modified the code to initialize the array as
color color_palette[100000];
and looped within bounds of array no problem. But with no. of
elem=1000000 the program again started crashing with wierd output at
gdb. I have earlier tried running a similar code to dump images in XPM
format but with vector class rather than arrays. That used to work
like anything.
If possible please help me understand the reason behind this problem
so that I can avoid it in future.
Thanks & Sincerely,
Madhur Kashyap
Code Snippet
===========
// Define 24-bit true colors
#define NCOL_R 256
#define NCOL_G 256
#define NCOL_B 256
#define MAX_COLORS NCOL_R*NCOL_G*NCOL_B
struct color {
int red, green, blue;
};
// create color palette
color color_palette[MAX_COLORS]; <<<<<<< ERROR because of this.
for (i=0; i<NCOL_R; i++) {
for (j=0; j<NCOL_G; j++) {
for (k=0; k<NCOL_B; k++) {
color_palette[col].red=0xffff-dcol_r*i;
color_palette[col].green=0xffff-dcol_g*j;
color_palette[col].blue=0xffff-dcol_b*k;
col++;
}
}
}
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