Randomly invert/negate section of image

[Greenriver]

Hi,

 

I'm trying to invert a random section of an image. The only way I've thought of doing this in PHP, is to split the image up into sections using imagecopyresampled then negate one of the sections using the imagefilter IMG_FILTER_NEGATE. Then put them all back together using imagecopymerge. Now I have managed to get this working when negating the first section ($split_first), but whenever I try to negate any other section (e.g. $split_sec) nothing happens. Now I know my code doesn't randomly invert it, I'm just trying to get it to work for each section first then I'll try get that working. Below I have posted my code.

 

Any help would be be appreciated,

 

Thank you in advance!

 

<?php
$image=imagecreate(400, 100);
$red = imagecolorallocate($image, 255, 0, 0);
imagefill($image, 0, 0, $red);
$split_first=imagecreate(100, 100);
$split_sec=imagecreate(100, 100);
$split_thir=imagecreate(100, 100);
$split_four=imagecreate(100, 100);

imagecopyresampled($split_first,$image,0,0,0, 0,100,100,100,100);
imagecopyresampled($split_sec,$image,100,0,100,0,100,100,100,100);
imagecopyresampled($split_thir,$image,200,0,200,0,100,100,100,100);
imagecopyresampled($split_four,$image,300,0,300,0,100,100,100,100);


imagefilter($split_sec, IMG_FILTER_NEGATE);

imagecopymerge($image,$split_first,0,0,0,0,100,100,100);
imagecopymerge($image,$split_sec,100,0,100,0,0,100,100);
imagecopymerge($image,$split_thir,200,0,200,0,0,100,100);
imagecopymerge($image,$split_thir,300,0,300,0,0,100,100);

imagepng($image);
imagedestroy($image);
header('Content-Type: image/png');
echo $image;
?>

[litebearer]

Just a crazy idea...

 

1. create 2 png from original

2. negate png 1

3. make 3/4 of png 1 transparent

4. copy png 1 onto png 2

 

[Greenriver]

Hi,

 

Thank you for the help. The problem is that the image is not going to be plain colour like the one above (I'm just testing to get it working first) the image will be an actual photo and all of the image will need to be negated at one point, so that would mean I couldn't overwrite the second half with the first like in your idea.

[litebearer]

Perhaps like this? (I took original, cropped upper left 1/4, saved it, negated it, overlaid it back on original)

http://www.nstoia.com/sat/crop/xxx.php

[Greenriver]

Hi there,

 

Yes that's it, I think that is currently what my code does above, but it only can do the first section, and no others. Does that negate any section of the image? As I can't seem to fathom it to negate every section of the image.

[litebearer]

easy enough to make it do what you want. are you going to negate each section the same?

 

[Greenriver]

Hi there,

 

Yeah so the idea is I have an image which is 400 x 100. I split it up into four sections each 100 x 100. Then select a section at random to negate. Thus far I've only been able to negate the first section, so the other three sections I can't get to negate. Thank you for your help!

[Greenriver]

So what would I need to change in my code to make it so $split_sec, $split_thir and $split_four can be inverted aswell?