Here is a small PHP function I wrote that emulates a gradient fill of an image.
Disclaimer : there are probably existing alternatives or classes, maybe in PEAR. I didn't check. I wanted to write a function myself, as part of my GD training grounds.
Usage
The function is packaged as a PHP class, the code you need is something like :
-
require_once('/path/to/gd-gradient-fill.php');
-
$image = new gd_gradient_fill($width,$height,$direction,$startcolor,$endcolor,$step);
The class call needs 5 arguments and accepts an optional 6th :
- integer $width
Width of the image - integer $height
Height of the image - string $direction
The shape or direction of the gradient, which can be any of : vertical, horizontal, ellipse, ellipse2, circle, circle2, rectangle, diamond. - string $startcolor
Gradient start color, 3 or 6 digit hexadecimal ("#ff0" or "#dd4578") - string $endcolor
Gradient end color - Optional : $step
Breaks the gradient smooth blending
Results
Here are a few examples of gradients from color #101040 to #a1a1ff. Hover the image for some unnecessary explanation.
Of course, the function handles non-square images just fine as well.
Get the function
- gd-gradient-fill.txt (download and save as .php)
- gd-gradient-fill.php (highlighted code, copy and paste in a blank file, but do not download as is)
Credits
I started from file header-img.php, part of Wordpress core file, which contains a similar hack to draw a gradient fill from lines. I believe this smart code is from Andy Skelton.
If you happen to use this function in any project, be sure to let me know. This makes my day :)
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commented, on 18/Feb/10 at 5:54 pm # :
Any example of handling non-square image using this function? I have a rounded corner image and would like to use this function to get the gradient effect. Thanks.
wrote, on 19/Dec/09 at 3:17 am # :
Ah, jumped the gun.
just needed to add these to the fill method:
imagealphablending($im, false);
imagesavealpha($im, true);
Works like a charm!
commented, on 19/Dec/09 at 3:08 am # :
Ozh-
Great piece of code. Anyway you can post a fix to get transparency? I thought I could just change imagecolorallocate to imagecolorallocatealpha and pass 0-127, but it's not working. I know it's in truecolor mode and I can generate transparent PNGs with imagefill.
Any ideas? Thanks!
said, on 01/Dec/09 at 2:22 am # :
I may be the last one to the party, but boy, am I enjoying myself! Fantastic class, and to mirror the comments above, written in '06 and going strong in '09.
Any chance for the updated code guys?
thx
thought, on 20/Oct/09 at 7:05 pm # :
Is there a chance to get the class with the transparency option?
This could help me very much.
Thank you very much in advance.
Best Regards
Stefan
replied, on 09/Oct/09 at 4:35 pm # :
Amendment to work on my server,
because of the "Notice - undefined variable.
line 190
/ / Marcus Alteracao
$ r = isset ($ r)? $ r: NULL;
$ g = isset ($ g)? $ g: NULL;
$ b = isset ($ b)? $ b: NULL;
Congratulations for the class and initiative.
Marcus Sá
Brazil
wrote, on 25/Sep/09 at 8:08 pm # :
Ok, the refactoring to add the ability to use "transparent" as the starting or ending color is done.
Ozh, I'll email you the revised code for review and posting.
replied, on 23/Sep/09 at 12:58 am # :
Great tool!
A transparency option would be nice though. I'm still new at php scripting, but shouldn't it be possible to pass a special value for the either of the color codes (start color or end color) so that the functions recogize that value as indicating "transparent"?
For example, instead of using #ff0000 and #0000ff to fade from red to blue, you could use #ff0000 and "transparent" to fade from red to transparent. The color values would have to be checked for the "transparent" value some time before the call to hex2rgb. Also, the fill function would have to be modified accordingly.
commented, on 13/Aug/09 at 3:24 pm # :
Nicely done. However, I removed the $this->display from the class constructor so that I can choose to grab the image $obj->image; instead for further processing.
Very nice function, written in '06, still standing in '09.
replied, on 04/Aug/09 at 5:32 pm # :
nico » You're right about the alt stuff. Fixed!