我开发了一个图像调整大小&使用PHP GD库修剪类.我在第一步中使用skibulks image trim script修剪图像背景,并在第二步中将图像缩放到所需尺寸(保持原始比例).

问题：从$this-> _trimBackground()函数获取新修剪的图像尺寸后,是否真的有必要进行第一次图像复制作业,以便首先通过带有新修剪尺寸的imagecopy重新创建图像(并在之后再次调整大小)？或者,是否可以将此作业与以下调整大小部分imagecopyresampled合并？

是否还有其他可能的性能改进,我不知道？欢迎各种表现建议！

功能1：

/**
 * Resize image file
 * 
 * @param   string $filepath the image filepath
 * @param   integer $width the width to resize
 * @param   integer $height the height to resize
 * @return  (image blob|boolean status)
 * @throws  Asset_Model_Image_Exception
 */
private function _resizeImageByFilepathAndReturn($filepath, $width, $height) {

    list($imageWidth, $imageHeight, $imageType) = getimagesize($filepath);

   switch($imageType) {
    case IMAGETYPE_GIF:
            $gdImage = imagecreatefromgif($filepath);
            break;
      case IMAGETYPE_JPEG:
            $gdImage = imagecreatefromjpeg($filepath);
            break;
      case IMAGETYPE_PNG:
            $gdImage = imagecreatefrompng($filepath);
            break;
      default:
                return false;
   }

   if($box = $this->_trimBackground($gdImage)) {

    $gdTrimmed = imagecreatetruecolor($box['w'], $box['h']);
    imagecopy($gdTrimmed, $gdImage, 0, 0, $box['l'], $box['t'], $box['w'], $box['h']);

    $imageWidth = $box['w'];
    $imageHeight = $box['h'];
    $gdImage = $gdTrimmed;

    unset($gdTrimmed);

   }

   if($imageWidth <= $width && $imageHeight <= $height) {

    $fwidth = $imageWidth;
        $fheight = $imageHeight;

   } else {

        $wscale = $width / $imageWidth;
        $hscale = $height / $imageHeight;
        $scale = min($wscale, $hscale);
        $fwidth = $scale * $imageWidth;
        $fheight = $scale * $imageHeight;

   }

   $gdThumbnail = imagecreatetruecolor($width, $height);

   imagefill($gdThumbnail, 0, 0, 0x00FFFFFF);

   imagecopyresampled($gdThumbnail, $gdImage, ($width - $fwidth) / 2, ($height - $fheight) / 2, 0, 0, $fwidth, $fheight, $imageWidth, $imageHeight);

   ob_start();
   imagejpeg($gdThumbnail, null, 90);
   $image = ob_get_contents();
   ob_end_clean();

   imagedestroy($gdImage);
   imagedestroy($gdThumbnail);

   return $image;

}

功能2：

/**
 * Trim image background
 * 
 * @param $gdImage image ressource
 */
private function _trimBackground($gdImage){

    $hex = imagecolorat($gdImage, 0,0);

    $width = imagesx($gdImage);
    $height = imagesy($gdImage);

    $bTop = 0;
    $bLft = 0;
    $bBtm = $height - 1;
    $bRt = $width - 1;

    for(; $bTop < $height; ++$bTop) {
        for($x = 0; $x < $width; ++$x) {
            if(imagecolorat($gdImage, $x, $bTop) != $hex) {
                break 2;
            }
        }
    }

    if($bTop == $height) {
        return false;
    }

    for(; $bBtm >= 0; --$bBtm) {
        for($x = 0; $x < $width; ++$x) {
            if(imagecolorat($gdImage, $x, $bBtm) != $hex) {
                break 2;
            }
        }
    }

    for(; $bLft < $width; ++$bLft) {
        for($y = $bTop; $y <= $bBtm; ++$y) {
            if(imagecolorat($gdImage, $bLft, $y) != $hex) {
                break 2;
            }
        }
    }

    for(; $bRt >= 0; --$bRt) {
        for($y = $bTop; $y <= $bBtm; ++$y) {
            if(imagecolorat($gdImage, $bRt, $y) != $hex) {
                break 2;
            }
        }
    }

    $bBtm++;
    $bRt++;

    return array('l' => $bLft, 't' => $bTop, 'r' => $bRt, 'b' => $bBtm, 'w' => $bRt - $bLft, 'h' => $bBtm - $bTop);

}

解决方法:

imagecopy()将$gdImage的一部分复制到$gdTrimmed,稍后几行用$gdTrimmed覆盖$gdImage.

Is it really necessary to do the first imagecopy?

这是你应该问自己的事情.

使用imagedestroy()函数而不是unset()可能会大大提高您的性能.这是对imagedestroy()的有用评论：

Reusing an image variable does NOT clear the old data out of memory!
You must use imagedestroy() to clear the data out. (I don’t know if
unset() works as well).

Also note that the image data in memory is raw, so don’t base how much
memory you are using based on the original filesize of the compressed
image (such as jpeg or png).