Hi,
On 22 Dec 2004, at 8:37, Siva Chandra wrote:
What exactly does the close() function do? For example, I might want to create a temporary image, ie. a temporary instance of pngwriter, but I do not want to save this image to a file. So then, can I just skip calling the close() function.
Yes, that is correct. All it does is go through the process of writing the file. You can call close(), modify the file (with plot() ), rename the file (with pngwriter_rename() ) and close() the instance again, and you'll have two different png files waiting for you.
Also, if I just want to create an image(again, an instance of pngwriter) which I do not intend to save to a file, then which constrcutor should I use for such purposes?
Any you want, really, it is irrelevant. Here are the constructors available:
1 pngwriter();
2 pngwriter(const pngwriter &rhs);
3 pngwriter(int width, int height, int backgroundcolour, char * filename);
4 pngwriter(int width, int height, double backgroundcolour, char * filename);
5 pngwriter(int width, int height, int backgroundcolour, const char * filename);
6 pngwriter(int width, int height, double backgroundcolour, const char * filename);
You may or may not know the size of the image. If you do, use any of 3 to 6. If you don't, you can either use 1 (the default constructor creates a PNGwriter instance that is 250x250, white background, and filename "out.png"), though this is not too efficient, or again any of 3 to 6, but with width and height set to 1 pixel. When you do finally know what size the image will be, you would then use resize().
I do not intend to create an image by reading from an existing file either!
That is not a problem, as the only time you use an existing file is when you use readfromfile().
Or, is it that both the above tasks are not possible?
They are quite possible! I hope I answered your questions.
Cheers,
Paul Blackburn
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