As I understood the task: you need to add a watermark to the original image, while changing its size relative to the original, without losing its proportionality.

Error (to the point)

Your mistake was that you tried to stretch the image of your watermark on 2 axes at once (x and y) . As I understand, the original images will be of different sizes, and the likelihood that 30% of both the width and the height will give you a proportional watermark is extremely small.

Decision

Do not chase after two hares and build your code on 2 axes. It is better to take only one and change the size of the watermark by leaning on it, after which we calculate the coefficient of this change and, while already running on it, work with the opposite axis.

Comment

In the examples below, the GD library functions will be used. For them to work, it must be present in your php. About GD can be found here: http://php.net/manual/ru/image.setup.php

Example

We get the image we need and the basis for the watermark.

 $im = imagecreatefromjpeg('1.jpg'); //Основное изображение $wm_source = imagecreatefrompng('2.png'); //Изображение ватермарки 

Find out the width and height of images of interest to us.

 $im_width = imagesx($im); //Ширина изображения $im_height = imagesy($im); //Высота изображения $wm_source_width = imagesx($wm_source); //Ширина основы ватермарки $wm_source_height = imagesy($wm_source); //Высота основы ватермарки 

And now the fun part. We calculate the new width for our watermark, relative to the width of the original image. It will be exactly 30% of the width of the original image.

 $wm_width = ($im_width / 100) * 30; //Ширина резайзнутой ватермарки (30% от изображения) 

After that, we calculate the coefficient of change of the width of our watermark, dividing its size (obtained slightly higher) by the size of its base.

 $co = $wm_width / $wm_source_width; //Коэффициент изменения 

And already with the help of this coefficient, we calculate the height of our watermark.

 $wm_height = $wm_source_height * $co; //Высота ватермирки 

Thus, we could not lose the proportionality of the watermark and meet the limit of 30% of the image. To put it in a simple way: we just took and changed the height of the watermark exactly by the same amount and changed its width, without losing proportionality there.

After all, if you multiply 2 numbers by the same thing, their relationship will not change, and this is proportionality.

Now let us indicate where our watermark will be located, in this case the lower left corner of the original image is taken. (no one bothers you choose another)

 $wm_x = $im_width - $wm_width; //Позиция x ватермарки $wm_y = $im_height - $wm_height; //Позиция y ватермарки 

Create the image itself for our watermark. It is worth noting that $ wm_source is a template, the basis, the original image of our watermark, while $ wm will be what we add to the image we need.

 $wm = imagecreatetruecolor($wm_width,$wm_height); //Создаём новую ватермарку 

Change the size of the watermark, with the parameters that we defined earlier.

 imagecopyresampled($wm,$wm_source,0,0,0,0,$wm_width,$wm_height,$wm_source_width,$wm_source_height); //Изменяем размер ватермарки 

We insert the watermark on the image we need.

 imagecopy($im,$wm,$wm_x,$wm_y,0,0,$wm_width,$wm_height); //Вставляем ватермарку 

Conclusion

That's all, I hope I helped in solving your problem. Below I will attach the full program code so you can run it without any problems. This is my first answer to StackOverflow, and I could be mistaken somewhere or ignore something, if this is true, then point out my mistakes, please.

Full program code

 header('Content-Type: image/png'); $im = imagecreatefromjpeg('1.jpg'); //Основное изображение $wm_source = imagecreatefrompng('2.png'); //Изображение ватермарки $im_width = imagesx($im); //Ширина изображения $im_height = imagesy($im); //Высота измениния $wm_source_width = imagesx($wm_source); //Ширина основы ватермарки $wm_source_height = imagesy($wm_source); //Высота основы ватермарки $wm_width = ($im_width / 100) * 30; //Ширина резайзнутой ватермарки (30% от изображения) $co = $wm_width / $wm_source_width; //Коофицент изменения $wm_height = $wm_source_height * $co; //Высота ватермирки $wm_x = $im_width - $wm_width; //Позиция x ватермарки $wm_y = $im_height - $wm_height; //Позиция y ватермарки $wm = imagecreatetruecolor($wm_width,$wm_height); //Создаём новую ватермарку imagecopyresampled($wm,$wm_source,0,0,0,0,$wm_width,$wm_height,$wm_source_width,$wm_source_height); //Изменяем размер ватермарки imagecopy($im,$wm,$wm_x,$wm_y,0,0,$wm_width,$wm_height); //Вставляем ватермарку imagepng($im); //Выводим результат