Pierre Joye skrev:
> hi,
> 
> On Tue, Jun 10, 2008 at 6:04 PM, ShadowRoze <roze@laun.se> wrote:
>> Hi, I would like to request that you add binary support for running Bicubic
>> image resizing. Currently I only have a PHP code snippet, taking approx 20
>> seconds to resize a 2000x1000px image to 550x275px.
> 
> For scaling images, is it really better than imagecopyresampled?
> 
>> I would like you to try speeding up this function, since 20 seconds is quite
>> much, and the current functions does look quite bad.
> 
>> http://pastebin.com/m216c7c32   <-- the function I'm using.
> 
> A couple of things that may help to speed up a bit your script:
> - if you load jpeg, drop the imagecolorforindex alltogether, jpeg are
> always truecolor (create two loops)

I load the following types with the script utilizing the function: jpeg, 
gif, png.
Not using ImageColorsForIndex results in having to use bitshifting instead.

> - don't allocate the color, simply calculate it once and use it with
> setpixel (0xAARRGGBB where AA goes from 0..127, other 0..255) save w*h
> function calls
> - truecolor image has no palette, no need to copy it (save a function call)
> -  calculate ($w - $ow) (and its $h equivalent) outside the loops, php
> does not optimize this part

After trying to implement all your suggestions the time required 
increased with 50% (ergo, to 30s).

> 
> And more generally, why don't you use a simpler algorithm for
> stretching images? Bicubic is good for scaling images (> 1.0x) but is
> not particullary good or fast for reducing images. A area weight
> implementation is fast and can give almost the best result
> (speed/quality ratio is good too).
> 
> About adding new interpolations (besides copyresampled), it is in
> progress, I have working code already. The C API provides the
> following methods (classic and a couple of optimized versions):
> 
> http://pierre.libgd.org/affine/api/files/src/gd-h.html#gdInterpolationMethod

Guess I'll have to wait for that one then.

> 
> I'm also planing to add MMX/SSE2 version as well. These new features
> should be in php 5.3.
> 
> Cheers,