PNG的透明背景保存为黑色_course

<div class="post-text" itemprop="text"> <p>I recently followed <a href="http://net.tutsplus.com/tutorials/php/image-resizing-made-easy-with-php/" rel="nofollow">this</a> tutorial, but the thing is when I save a PNG it has a solid black background?.. I am rather new to php.. how do I save it with a transparent background?</p> <p>Here's the php class:</p> <pre><code># include("classes/resize_class.php"); # $resizeObj = new resize('images/cars/large/input.jpg'); # $resizeObj -&gt; resizeImage(150, 100, 0); # $resizeObj -&gt; saveImage('images/cars/large/output.jpg', 100); Class resize { // *** Class variables private $image; private $width; private $height; private $imageResized; function __construct($fileName) { // *** Open up the file $this-&gt;image = $this-&gt;openImage($fileName); // *** Get width and height $this-&gt;width = imagesx($this-&gt;image); $this-&gt;height = imagesy($this-&gt;image); } ## -------------------------------------------------------- private function openImage($file) { // *** Get extension $extension = strtolower(strrchr($file, '.')); switch($extension) { case '.jpg': case '.jpeg': $img = @imagecreatefromjpeg($file); break; case '.gif': $img = @imagecreatefromgif($file); break; case '.png': $img = @imagecreatefrompng($file); break; default: $img = false; break; } return $img; } ## -------------------------------------------------------- public function resizeImage($newWidth, $newHeight, $option="auto") { // *** Get optimal width and height - based on $option $optionArray = $this-&gt;getDimensions($newWidth, $newHeight, $option); $optimalWidth = $optionArray['optimalWidth']; $optimalHeight = $optionArray['optimalHeight']; // *** Resample - create image canvas of x, y size $this-&gt;imageResized = imagecreatetruecolor($optimalWidth, $optimalHeight); imagecopyresampled($this-&gt;imageResized, $this-&gt;image, 0, 0, 0, 0, $optimalWidth, $optimalHeight, $this-&gt;width, $this-&gt;height); // *** if option is 'crop', then crop too if ($option == 'crop') { $this-&gt;crop($optimalWidth, $optimalHeight, $newWidth, $newHeight); } } ## -------------------------------------------------------- private function getDimensions($newWidth, $newHeight, $option){ switch ($option) { case 'exact': $optimalWidth = $newWidth; $optimalHeight= $newHeight; break; case 'portrait': $optimalWidth = $this-&gt;getSizeByFixedHeight($newHeight); $optimalHeight= $newHeight; break; case 'landscape': $optimalWidth = $newWidth; $optimalHeight= $this-&gt;getSizeByFixedWidth($newWidth); break; case 'auto': $optionArray = $this-&gt;getSizeByAuto($newWidth, $newHeight); $optimalWidth = $optionArray['optimalWidth']; $optimalHeight = $optionArray['optimalHeight']; break; case 'crop': $optionArray = $this-&gt;getOptimalCrop($newWidth, $newHeight); $optimalWidth = $optionArray['optimalWidth']; $optimalHeight = $optionArray['optimalHeight']; break; } return array('optimalWidth' =&gt; $optimalWidth, 'optimalHeight' =&gt; $optimalHeight); } ## -------------------------------------------------------- private function getSizeByFixedHeight($newHeight) { $ratio = $this-&gt;width / $this-&gt;height; $newWidth = $newHeight * $ratio; return $newWidth; } private function getSizeByFixedWidth($newWidth) { $ratio = $this-&gt;height / $this-&gt;width; $newHeight = $newWidth * $ratio; return $newHeight; } private function getSizeByAuto($newWidth, $newHeight) { if ($this-&gt;height &lt; $this-&gt;width) // *** Image to be resized is wider (landscape) { $optimalWidth = $newWidth; $optimalHeight= $this-&gt;getSizeByFixedWidth($newWidth); } elseif ($this-&gt;height &gt; $this-&gt;width) // *** Image to be resized is taller (portrait) { $optimalWidth = $this-&gt;getSizeByFixedHeight($newHeight); $optimalHeight= $newHeight; } else // *** Image to be resized is a square { if ($newHeight &lt; $newWidth) { $optimalWidth = $newWidth; $optimalHeight= $this-&gt;getSizeByFixedWidth($newWidth); } else if ($newHeight &gt; $newWidth) { $optimalWidth = $this-&gt;getSizeByFixedHeight($newHeight); $optimalHeight= $newHeight; } else { // *** Sqaure being resized to a square $optimalWidth = $newWidth; $optimalHeight= $newHeight; } } return array('optimalWidth' =&gt; $optimalWidth, 'optimalHeight' =&gt; $optimalHeight); } ## -------------------------------------------------------- private function getOptimalCrop($newWidth, $newHeight) { $heightRatio = $this-&gt;height / $newHeight; $widthRatio = $this-&gt;width / $newWidth; if ($heightRatio &lt; $widthRatio) { $optimalRatio = $heightRatio; } else { $optimalRatio = $widthRatio; } $optimalHeight = $this-&gt;height / $optimalRatio; $optimalWidth = $this-&gt;width / $optimalRatio; return array('optimalWidth' =&gt; $optimalWidth, 'optimalHeight' =&gt; $optimalHeight); } ## -------------------------------------------------------- private function crop($optimalWidth, $optimalHeight, $newWidth, $newHeight) { // *** Find center - this will be used for the crop $cropStartX = ( $optimalWidth / 2) - ( $newWidth /2 ); $cropStartY = ( $optimalHeight/ 2) - ( $newHeight/2 ); $crop = $this-&gt;imageResized; //imagedestroy($this-&gt;imageResized); // *** Now crop from center to exact requested size $this-&gt;imageResized = imagecreatetruecolor($newWidth , $newHeight); imagecopyresampled($this-&gt;imageResized, $crop , 0, 0, $cropStartX, $cropStartY, $newWidth, $newHeight , $newWidth, $newHeight); } ## -------------------------------------------------------- public function saveImage($savePath, $imageQuality="100") { // *** Get extension $extension = strrchr($savePath, '.'); $extension = strtolower($extension); switch($extension) { case '.jpg': case '.jpeg': if (imagetypes() &amp; IMG_JPG) { imagejpeg($this-&gt;imageResized, $savePath, $imageQuality); } break; case '.gif': if (imagetypes() &amp; IMG_GIF) { imagegif($this-&gt;imageResized, $savePath); } break; case '.png': // *** Scale quality from 0-100 to 0-9 $scaleQuality = round(($imageQuality/100) * 9); // *** Invert quality setting as 0 is best, not 9 $invertScaleQuality = 9 - $scaleQuality; if (imagetypes() &amp; IMG_PNG) { imagepng($this-&gt;imageResized, $savePath, $invertScaleQuality); } break; // ... etc default: // *** No extension - No save. break; } imagedestroy($this-&gt;imageResized); } } ?&gt; </code></pre> <p>a lot of code i know.. but i wouldn't know which parts are vital..apologies...</p> <p>Any Help Greatly Appreciated.</p> </div>

Android实现bmp图片转换成jpg_course

由于BMP图片太大，imageview控件无法正常显示，所以我想把BMP图片先转换成jpg再进行显示，但由于刚刚接触不甚了解，请大神们帮帮我。。谢谢了