使用php生成Imagemagick缩略图 - 使用-crop [英] Imagemagick thumbnail generation with php - using -crop

问题描述

很久以前我创建了一个小型库来使用imagemagick通过 system（...）调整图像大小，因为我不觉得PHP的内置imagemagick函数是

Long ago I created a small library for resizing images using imagemagick through system(...) because I did not feel that the build-in imagemagick functions for PHP were sufficient.

然而，最近我不得不把它移植到symfony项目中，我选择使用sfThumbnailPlugin（如果我没记错的话）。遗憾的是，这不包括作物功能 - 即指定所需的大小，例如， 300x300像素并缩放缩略图使其适合。我自己选择实现这个功能，但似乎有些不对劲。

However, recently I had to port this to a symfony project and I chose to use sfThumbnailPlugin (if I remember correctly). This unfortunately didn't include the crop functionality - i.e. to specify a desired size, e.g. 300x300 px and have the thumbnail cropped so that it fit. I chose to implement this functionality myself, but there seems to be something wrong.

每当我将图像调整到所需大小时，宽度大于高度，比例搞砸了。请看一下这个例子： http://i37.tinypic.com/9hkqrl.png - 在此示例中，顶行是正确的比例，底行是问题。

Whenever I resize an image to a desired size there whe width is greater than the height, the proportions get screwed. Take a look at this example: http://i37.tinypic.com/9hkqrl.png - In this example the top row is the correct proportions and the bottom row is the problem.

在示例中，顶部和底部应该被裁剪。

In the example, the top and bottom should have been cropped.

以下是完成裁剪的部分的代码（变量名称应该是不言自明的）：

Here is the code for the part where the crop is done (the variable names should be self-explanatory):

<?php
    if ($width/$height > $this->maxWidth/$this->maxHeight) {
      // then resize to the new height...
                $command .= ' -resize "x'.$this->maxWidth.'"';

                // ... and get the middle part of the new image
                // what is the resized width?
                $resized_w = ($this->maxWidth/$height) * $width;

                // crop
                $command .= ' -crop "'.$this->maxHeight.'x'.$this->maxWidth.'+'.round(($resized_w - $this->maxWidth)/2).'+0"';
            } else {
                // or else resize to the new width
                $command .= ' -resize "'.$this->maxHeight.'x"';

                // ... and get the middle part of the new image
                // what is the resized height?
                $resized_h = ($this->maxHeight/$width) * $height;

                // crop
                $command .= ' -crop "'.$this->maxWidth.'x'.$this->maxHeight.
                             '+0+'.round(($resized_h - $this->maxHeight)/2).'" +repage';
            }

这是产生错误代码的if语句的第二部分。

Is is the second part of the if statement that produces the wrong code.

任何人都可以为我纠正这个问题吗？显然计算错误。

Can anyone correct this for me? Obviously the calculations are wrong.

推荐答案

解决方案如下：

    if ($width/$height > $this->maxWidth/$this->maxHeight) {
      // then resize to the new height...
                $command .= ' -resize "x'.$this->maxHeight.'"';

                // ... and get the middle part of the new image
                // what is the resized width?
                $resized_w = ($this->maxHeight/$height) * $width;

                // crop
                $command .= ' -crop "'.$this->maxWidth.'x'.$this->maxHeight.'+'.round(($resized_w - $this->maxWidth)/2).'+0" +repage';
            } else {
              $command .= ' -resize "' . $this->maxWidth . 'x"';
              $resized_h = ($this->maxWidth/$width) * $height;

                // crop
                $command .= ' -crop "'.$this->maxWidth.'x'.$this->maxHeight.
                             '+0+'.round(($resized_h - $this->maxHeight)/2).'" +repage';
            }

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