php圖片透明

❶ phpcms png透明圖片裁剪後變成黑底請各位高手給出解決方式

1、png透明圖片，裁剪後不會變成黑底。
2、即使有意把圖層合並了，它也是白色的背景，不可能變成黑色背景。

❷ php如何判斷圖片是透明圖

用php的擴張imagick 來做 getImageAlphaChannel方法來判斷

❸ php怎麼輸出背景透明的圖片

php可以使用GD庫或者ImageMagick工具生成png或者gif的背景透明圖片.推薦使用ImageMagick.
這里有範例 http://php.net/manual/en/imagick.examples-1.php
准備一張png圖片,放到php文件的目錄,運行看看效果.
<?php
/* Read the image */
$im = new Imagick("test.png");
/* Thumbnail the image */
$im->thumbnailImage(200, null);

/* Create a border for the image */
$im->borderImage(new ImagickPixel("white"), 5, 5);

/* Clone the image and flip it */
$reflection = $im->clone();
$reflection->flipImage();

/* Create gradient. It will be overlayed on the reflection */
$gradient = new Imagick();

/* Gradient needs to be large enough for the image and the borders */
$gradient->newPseudoImage($reflection->getImageWidth() + 10, $reflection->getImageHeight() + 10, "gradient:transparent-black");

/* Composite the gradient on the reflection */
$reflection->compositeImage($gradient, imagick::COMPOSITE_OVER, 0, 0);

/* Add some opacity. Requires ImageMagick 6.2.9 or later */
$reflection->setImageOpacity( 0.3 );

/* Create an empty canvas */
$canvas = new Imagick();

/* Canvas needs to be large enough to hold the both images */
$width = $im->getImageWidth() + 40;
$height = ($im->getImageHeight() * 2) + 30;
$canvas->newImage($width, $height, new ImagickPixel("black"));
$canvas->setImageFormat("png");

/* Composite the original image and the reflection on the canvas */
$canvas->compositeImage($im, imagick::COMPOSITE_OVER, 20, 10);
$canvas->compositeImage($reflection, imagick::COMPOSITE_OVER, 20, $im->getImageHeight() + 10);

/* Output the image*/
header("Content-Type: image/png");
echo $canvas;
?>