imagetotxt php,PHP将iTXt注释添加到PNG图像

迈不过友情╰ 2022-08-30 09:10 125阅读 0赞

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I have looked around for this everywhere. I know it can be done using some libraries in .net, but I really want my script to generate a "marked" image. The reason is that we are a forum host, and have teamed up with a theme making company. The theme making company wants us to be able to track down any illegally distributed themes. I saw the iTXt comment in the GCHQ CanYouCrackIt exercise and think it'll be the best, no intrusive method of protecting our property.

解决方案

A suggestion: If you have a fixed iTXt chunk that you want to add to an image, a quick and dirty procedure could be to simply insert it just before the IEND chunk (12 bytes) of the original image. This should work, because the iTXt can be placed before of after the image data. Of course, this does not check if the chunk as already there.

Here's an example code, using the tEXt chunk (slightly simpler), it needs some polishing but it basically works:

addTextToPngFile("x.png","x2.png","Watermark","Hi this is a TEXT test");

function addTextToPngFile($pngSrc,$pngTarget,$key,$text) \{

$chunk = phpTextChunk($key,$text);

$png = file\_get\_contents($pngSrc);

$png2 = addPngChunk($chunk,$png);

file\_put\_contents($pngTarget,$png2);

// creates a tEXt chunk with given key and text (iso8859-1)

// ToDo: check that key length is less than 79 and that neither includes null bytes

function phpTextChunk($key,$text) \{

$chunktype = "tEXt";

$chunkdata = $key . "\\0" . $text;