将CSS滤镜的亮度转换为PHP IMG_FILTER_BRIGHTNESS

问题描述

我的页面上有一张图片，下面有一个 HTML 范围滑块.当我移动滑块时，一些 jQuery 会更改图像的 CSS 过滤器亮度.

I have an image on my page with a HTML range slider below. When I move the slider, a bit of jQuery changes the CSS filter brightness of the image.

所以我可以例如使用 CSS 将亮度降低10％，20％，将亮度增加一倍至200％，等等.

so I can for example get CSS to reduce the brightness by 10%, 20%, double the brightness to 200% etc. That works fine.

我希望** PHP **(GD)使用IMG_FILTER_BRIGHTNESS应用亮度更改.问题是IMG_FILTER_BRIGHTNESS不使用百分比，它对100％使用0，对于纯白色使用255，对于纯黑色使用-255.

I want **PHP **(GD) to apply the brightness changes using IMG_FILTER_BRIGHTNESS. The problem is IMG_FILTER_BRIGHTNESS doesn't use percentages, it uses 0 for 100%, 255 for pure white and -255 for pure black.

有人知道我如何将滑块上选择的值转换为 PHP 所需的相应值吗?

Does anyone know how I can convert the value chosen on the slider to the corresponding value needed for PHP?

推荐答案

假定范围的相关性如下:

Assuming that the ranges correlate like so:

     | black | no change | white
-----|-------+-----------+-------
 CSS |     0 |         1 |     2
-----+-------+-----------+-------
 PHP |  -255 |         0 |   255

您可以在PHP中进行简单的计算:

You can make a simple calculation in PHP:

$brightness = (255 - (255 * $css)) * -1;

结果:

• 如果$css == 1(100％)，则$brightness == 0.
• 如果$css == 0(0％)，则$brightness == -255.
• 如果$css == .5(50％)，则$brightness == -127.5.
• 如果$css == 1.2(120％)，则$brightness == 51.

• If $css == 1 (100%) then $brightness == 0.
• If $css == 0 (0%) then $brightness == -255.
• If $css == .5 (50%) then $brightness == -127.5.
• If $css == 1.2 (120%) then $brightness == 51.

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