Re: Re: GD library and PHP

Speaking of GD, there is a very troubling problem that I have never found a straight answer to. The imagettfbbox function uses the baseline of the font for it's bounding box. What good is a bounding box without the decenders? Now if this were a simple calculation it wouldn't be so bad, but that doesn't seem to be the case. I have yet to be able to (or find an example of) calculating an accurate bounding box for any given text/font/angle/pointsize right down to the pixel on every side. Some come close, but that's not acceptible to a web page designer ;-) Is this a problem with GD itself, or something with the font files, or PHP's imagettfbox functionality? Is this something that could be "fixed"? TIA Monte Sterling Hughes wrote:

Dmitry, Sorry, for the length of my reply, and now the fact that I'm just refferring you to another source. I'm actually not responsible for the gd library (at least since I last checked :). Your help would definitely be appreciated, I've forwarded this request to php-dev@lists.php.net which is the developers mailing list. If you would like to work on the gd extension, please feel free to apply for a cvs account at: http://www.php.net/cvs-php.php Thanks, Sterling

Hello, I have recently learned that GD library is being integrated into PHP, and apparently you have some relation to that. While GD library has a very good set of functions, the implementation is very poor in my opinion. The code is quite redundant and un-optimized in any way. This probably has to be addressed to the author of GD, but since it is now going to be part of PHP, may be some apparent optimization can be applied to the bundled version. My concerns raised when I tried to use ImageCopyResampled function. It nearly brings my server to its knees due to high memory and processor usage (when running 15-20 Apache processes each processing some image via ImageCopyResampled in PHP). The processing time is also very high - typically around 10 seconds for 1 calls to ImageCopyResampled with 1-2 megapixel images. Of course, those numbers relate to my server, people with faster computers may get better results. By in any case, I decided to look into implementation of gdImageCopyResampled in GD library and saw lots of this that can be improved. I did not look into other function, but I suspect this is true for the whole GD library. The function uses brute force approach and many values that can be calculated in the outer loop or outside of any loops are being calculated in the inner loop. E.g. sy1 = ((float) y - (float) dstY) * (float) srcH / (float) dstH; sy2 = ((float) (y + 1) - (float) dstY) * (float) srcH / (float) dstH; is being calculated for each x, while it really needs to be calculated for each y. This part is a constant: (float) dstY * (float) srcH / (float) dstH and therefore can be calculated once per call, not dstW*dstH*2 times. Similarly, int pd = gdImageGetPixel (dst, x, y); is being called inside of the inner loop (dstW*dstH times!) = but is not being used anywhere later! Applying some apparent mathematics, we can calculate the final spixels value in one easy step, rather than using (potentially) multiple floating point additions and multiplications in the inner loop (spixels += xportion * yportion). Instead total spixels value for the current (x,y) can be found as spixels = (y2-y1)* (x2-x1); // and, again, this can also be optimized further I can point out several other things that can be easily improved, but you got my point already. It is possible to reduce number of calculation dramatically, without breaking readability and/or compatibility. I am wondering if anyone is considering to do this any time soon. I would be more than willing to discuss my suggestions with someone responsible for this library, or even modify the code myself (a little bit harder for me, since I have little time to make extensive tests). Regards, Dmitry -- Dmitry Petrov phone: (212) 641-3235 pager: pagedp@nchcapital.com -- *** DISCLAIMER *** This message is intended only for the use of the individual or entity to which it is addressed and may contain information that is privileged, confidential and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this message in error, please notify the sender by reply transmission and delete the message. ------------------