计算宽度和高度，以调整图像大小 - Calculating width and height to resize image

我想计算图像的宽度和大小。我认为有三种情况:

1。图像宽度超过最大宽度限制:然后将图像宽度调整为最大宽度，并根据最大宽度限制计算高度。例如，图像宽度为2248，高度为532。宽度大于，高度小于。因此，将宽度减小到最大1024，并计算高度，它将在242左右。

2。图像高度超过最大高度限制:同样，将高度调整为最大高度，并相应地计算宽度。

3。高度和宽度都超过了最大高度和最大宽度:进一步处理，找出图像是垂直的还是水平的。如果图像是水平的，则将宽度调整为最大宽度并据此计算高度。否则，如果图像是垂直的或正方形的，则将高度调整为最大值，并根据该值计算宽度。

对于这些情况，你可以看看我下面的代码，给出你的专家意见，如果它有任何好处吗?还是可以改进?如何?

p。我昨天也问过类似的问题。在我之前的问题中，我不确定逻辑应该是什么，现在我知道它应该是什么(如上所述)，并且想知道它是否有任何好处。谢谢你的帮助。

<?
$max_width = 1024;
$max_height = 768;
$img = "t2.jpg";

list($original_width, $original_height) = getimagesize($img);
if (($original_width > $max_width) OR ($original_height > $max_height))
{
//original width exceeds, so reduce the original width to maximum limit.
//calculate the height according to the maximum width.
    if(($original_width > $max_width) AND ($original_height <= $max_height))
    {   
        $percent = $max_width/$original_width;  
        $new_width = $max_width;
        $new_height = round ($original_height * $percent);
    }
    //image height exceeds, recudece the height to maxmimum limit.
    //calculate the width according to the maximum height limit.
    if(($original_width <= $max_width) AND ($original_height > $max_height))
    {
        $percent = $max_height/$original_height;
        $new_height = $max_height;
        $new_width = round ($original_width * $percent);
    }
    //both height and width exceeds.
    //but image can be vertical or horizontal.
    if(($original_width > $max_width) AND ($original_height > $max_height))
    {
        //if image has more width than height
        //resize width to maximum width.
        if ($original_width > $original_height)
        {
            $percent = $max_width/$original_width;
            $new_width = $max_width;
            $new_height = round ($original_height * $percent );
        }
        //image is vertical or square. More height than width.
        //resize height to maximum height.  
        else
        {
        $new_height = $max_height;
        $percent = $max_height/$original_height;
        $new_height = $max_height;
        $new_width = round ($original_width * $percent);
        }
    }
} 
?>

// Usage example to find the proper dimensions to resize an image down to 300x400 pixels maximum: 
list($width, $height) = getimagesize($image); 
$new_dimensions = resize_dimensions(100,100,$width,$height);  

// Calculates restricted dimensions with a maximum of $goal_width by $goal_height 
function resize_dimensions($goal_width,$goal_height,$width,$height) { 
    $return = array('width' => $width, 'height' => $height); 
    // If the ratio > goal ratio and the width > goal width resize down to goal width 
    if ($width/$height > $goal_width/$goal_height && $width > $goal_width) { 
        $return['width'] = $goal_width; 
        $return['height'] = $goal_width/$width * $height; 
    } 
    // Otherwise, if the height > goal, resize down to goal height 
    else if ($height > $goal_height) { 
        $return['width'] = $goal_height/$height * $width; 
        $return['height'] = $goal_height; 
    } 
    return $return; 
}

我不懂PHP，但我会这样做(c++伪代码):

float ratio = 1.0;
float ratio_w = max_width/static_cast<float>(original_width);
float ratio_h = max_height/static_cast<float>(original_height);
float ratio_max = std::max(ratio_w, ratio_h);
if (ratio_max < 1.0)
{  
   // width & height are larger than allowed
   // scale to the larger scaling factor
   ratio = ratio_max;
}
else
{
   // pick a scaling factor <= 1.0
   ratio = std::min(ratio, ratio_w);
   ratio = std::min(ratio, ratio_h);
}
if (ratio < 1.0) // this if-clause is not necessary
{
   new_width = original_width * ratio;
   new_height = original_height * ratio;   
}

我编辑了我的代码以包含第三种情况，这是我之前忽略的。我通常尽量避免嵌套if语句，因为可读性(个人风格)和部分性能原因(主要是迷信;-))。

我不知道我的版本是否比原来的版本更快或更可读，但至少$new_width和$new_height的冗余赋值消失了。

使用相同的变量名和if语句防止升级:

<?php
$max_width = 1024;
$max_height = 768;
$img = "t2.jpg";

list($original_width, $original_height) = getimagesize($img);
$ratio = ($max_width / $original_width < $max_height / $original_height
  ? $max_width / $original_width
  : $max_height / $original_width
);
if ($original_width > $max_width || $original_height > $max_height) {
  $new_width = $original_width * $ratio;
  $new_height = $original_height * ratio;
} 
?>

我发现这是一个更优雅的放大或缩小的解决方案，如果你只想缩小，只需添加if($scale_percent<1) {}

<?php
$width  = $max_width = 400;
$height = $max_height = 400;
$size = getimagesize($img);
if(count($size)) {
    $width = $size[0];
    $height = $size[1];
    $width_percent = $max_width/$width;
    $height_percent = $max_height/$height;
    $scale = ($width_percent>$height_percent)?'height':'width';
    $scale_percent = $scale.'_percent';
    $scale_percent = $$scale_percent;   
    $width*=$scale_percent;
    $height*=$scale_percent;        
}
?>

有一个非常方便的类，我经常用于这类工作，在保持长宽比的同时调整图像的大小。它可以让你调整图像到给定的高度或宽度…

图片大小调整类

注意:您必须在该网站注册才能获得文件

获取width &图片的高度

$image_info = getimagesize($_FILES["file_field_name"]["tmp_name"]);
$image_width = $image_info[0];
$image_height = $image_info[1];