计算用于调整大小的图像大小比率

Question

我有一个定义的固定宽度和高度来调整图像大小。但是，我有问题，因为图像可以有任何类型的大小比例（可以是垂直或水平）。在这种情况下，固定的宽度和高度会引起问题。我想以更聪明的方式计算宽度和高度。

例如，假设我已经定义了宽度1024px和高度768px 。我想调整垂直（高度1100px和宽度200px）的图像。因此，在我的情况下，它会调整为固定的大小（1024x768），因此宽度将从 100px增加到768px ，这将非常难看。同样，如果图像的高度小于 768px ，则会强制将高度增加到 768px 。

因此，我想根据原始图像尺寸比率计算新的图像尺寸。让我们说如果上面的示例图像应该调整为 768px 的最大高度，但那么宽度呢？它已经小于我的“最大宽度”，即 200px ，那么宽度应保持不变吗？还是应该进一步减少？

同样，如果图像的高度为200px，宽度为1100px 。所以宽度应该降低到1024px ，但高度怎么样？

第三个问题是，假设高度和宽度都超过最大高度和最大宽度，我们假设宽度：1100px和高度：4000px 。现在，由于宽度和高度都超过最大宽度和最大高度，但图像是垂直的，它将使其成为水平。那么如何在这种情况下检查是否应该根据最大高度或根据最大宽度调整图像大小？

我很感激任何帮助。

Answer 1

这是我个人抓取图像大小调整代码的代码。首先，您需要的数据：

list($originalWidth, $originalHeight) = getimagesize($imageFile);
$ratio = $originalWidth / $originalHeight;

然后，该算法尽可能地将图像拟合到目标尺寸中，保持原始纵横比，而不是将图像拉伸得比原始尺寸大：

$targetWidth = $targetHeight = min($size, max($originalWidth, $originalHeight));

if ($ratio < 1) {
    $targetWidth = $targetHeight * $ratio;
} else {
    $targetHeight = $targetWidth / $ratio;
}

$srcWidth = $originalWidth;
$srcHeight = $originalHeight;
$srcX = $srcY = 0;

这会使图像完全填满目标尺寸，而不是拉伸它：

$targetWidth = $targetHeight = min($originalWidth, $originalHeight, $size);

if ($ratio < 1) {
    $srcX = 0;
    $srcY = ($originalHeight / 2) - ($originalWidth / 2);
    $srcWidth = $srcHeight = $originalWidth;
} else {
    $srcY = 0;
    $srcX = ($originalWidth / 2) - ($originalHeight / 2);
    $srcWidth = $srcHeight = $originalHeight;
}

这实际上是调整大小：

$targetImage = imagecreatetruecolor($targetWidth, $targetHeight);
imagecopyresampled($targetImage, $originalImage, 0, 0, $srcX, $srcY, $targetWidth, $targetHeight, $srcWidth, $srcHeight);

在这种情况下，$size只是宽度和高度（方形目标大小）的一个数字。我相信你可以修改它以使用非方形目标。它还应该为您提供可以使用的其他调整大小算法的灵感。

Answer 2

$ratio = $originalWidth / $originalHeight

如果你想改变高度：

$targetWidth = $targetHeight * $ratio

如果你想改变宽度：

$targetHeight = $targetWidth / $ratio

Answer 3

您想要的是保持原始图像的纵横比。这是图像的宽度和高度之间的比率。因此，您需要计算在垂直和水平方向上调整图像大小的因子，然后保持两者中的较高者。在伪代码中：

target_height = 768
target_width = 1024
# v_fact and h_fact are the factor by which the original vertical / horizontal
# image sizes should be multiplied to get the image to your target size.
v_fact = target_height / im_height 
h_fact = target_width / im_width
# you want to resize the image by the same factor in both vertical 
# and horizontal direction, so you need to pick the correct factor from
# v_fact / h_fact so that the largest (relative to target) of the new height/width
# equals the target height/width and the smallest is lower than the target.
# this is the lowest of the two factors
im_fact = min(v_fact, h_fact)
new_height = im_height * im_fact
new_width = im_width * im_fact
image.resize(new_width, new_height)

Answer 4

这是有效的。

function calculateDimensions($width,$height,$maxwidth,$maxheight)
{

        if($width != $height)
        {
            if($width > $height)
            {
                $t_width = $maxwidth;
                $t_height = (($t_width * $height)/$width);
                //fix height
                if($t_height > $maxheight)
                {
                    $t_height = $maxheight;
                    $t_width = (($width * $t_height)/$height);
                }
            }
            else
            {
                $t_height = $maxheight;
                $t_width = (($width * $t_height)/$height);
                //fix width
                if($t_width > $maxwidth)
                {
                    $t_width = $maxwidth;
                    $t_height = (($t_width * $height)/$width);
                }
            }
        }
        else
            $t_width = $t_height = min($maxheight,$maxwidth);

        return array('height'=>(int)$t_height,'width'=>(int)$t_width);
    }

Answer 5

您需要的是“保持”宽高比。 最初你有一个大小（wxh）500x1000的图像，这个宽高比是0.5。假设您将高度1000更改为768，则结果宽度将为0.5 * 768 = 384。

另一个示例1800 x 1200和新高度为200，那么您的新宽度为300，因为{{1} } {是300/200而1.5也是1800/1200。

祝你好运。

Answer 6

检查下面的php代码：

$new_width  = 1024;
$new_height = 768;
$this_image = "images/my_image";

list($width, $height, $type, $attr) = getimagesize("$this_image");

if ($width > $height) {
  $image_height = floor(($height/$width)*$new_width);
  $image_width  = $new_width;
} else {
  $image_width  = floor(($width/$height)*$new_height);
  $image_height = $new_height;
}
echo "<img src='$this_image' height='$image_height' width='$image_width'>";

Answer 7

您应该调整大小，具体取决于哪个属性远离最大值。然后，计算比率。

if(($w - $w_max) > ($h - $h_max)) {
    $w_new = $w_max;
    $h_new = (int) ($h * ($w_max / $w));
}
else {
    $h_new = $h_max;
    $w_new = (int) ($w * ($h_max / $h));
}

Answer 8

我达到了这个问题并没有找到合适的答案，所以我自己开始回答这个问题。

我从一些基本的逻辑开始，在咨询了我的一位在数学上更好的朋友之后，这就是我们想出来的。

function calculate_dimensions($width,$height,$max){
    if($width != $height){
        if($width > $height){
            $t_height = $max;
            $t_width = min(($width * $t_height)/$height);
        }
        if($height > $width){
            $t_width = $max;
            $t_height = min(($t_width * $height)/$width)
        }
    }else{
        if($width > $max){
            $t_width = $t_height = $max;
        }
    }
    $res = ['height'=>$t_height,'width'=>$t_width]
    return $res;
}

这段代码是可以重复使用的，所以要把自己搞定。只需传递允许的最大最小尺寸，它就会计算出最大边的尺寸，这样你就可以得到一个正确缩放的尺寸，然后你可以在其中居中裁剪，从而产生正确缩小和裁剪的图像方形图像。这对于个人资料图片和缩略图等内容很有用。

向我的朋友Justin Gillett表示他对交叉乘法的精彩建议。

Answer 9

此示例将缩小图像以适合定义的像素完美纵横比（16：9），从而创建不大于指定限制（1200 x 675）的图像。

设置图像比率和任何上限：

const RATIO_W                       = 16;
const RATIO_H                       = 9;
const RATIO_MULIPLIER_UPPER_LIMIT   = 75;

计算新图像宽度和高度

list($imageWidth, $imageHeight) = getimagesize($path_to_image);    

if( ($imageWidth / $imageHeight) === (self::RATIO_W / self::RATIO_H) ){
    return;

// Find closest ratio multiple to image size
if($imageWidth > $imageHeight){
    // landscape
    $ratioMultiple  = round($imageHeight / self::RATIO_H, 0, PHP_ROUND_HALF_DOWN);
}else{
    // portrait
    $ratioMultiple  = round($imageWidth / self::RATIO_W, 0, PHP_ROUND_HALF_DOWN);
}    

$newWidth   = $ratioMultiple * self::RATIO_W;
$newHeight = $ratioMultiple * self::RATIO_H;    

if($newWidth > self::RATIO_W * self::RATIO_MULIPLIER_UPPER_LIMIT|| $newHeight > self::RATIO_H * self::RATIO_MULIPLIER_UPPER_LIMIT){
    // File is larger than upper limit
    $ratioMultiple = self::RATIO_MULIPLIER_UPPER_LIMIT;
}    

$this->tweakMultiplier($ratioMultiple, $imageWidth, $imageHeight);    

$newWidth   = $ratioMultiple * self::RATIO_W;
$newHeight = $ratioMultiple * self::RATIO_H;    

调整图片大小

$originalImage  = imagecreatefromjpeg( $tempImagePath );
$newImage       = imagecreatetruecolor($newWidth, $newHeight);
imagefilledrectangle($newImage, 0, 0, $newWidth, $newHeight, imagecolorallocate($newImage, 255, 255, 255));
imagecopyresampled($newImage, $originalImage, 0, 0, 0, 0, $newWidth, $newHeight, $imageWidth, $imageHeight);
imagejpeg($newImage, $tempImagePath, 100);

循环通过因子直到两个尺寸都小于原始图像尺寸

protected function tweakMultiplier( &$ratioMultiple, $fitInsideWidth, $fitInsideHeight ){
    $newWidth   = $ratioMultiple * self::RATIO_W;
    $newHeight  = $ratioMultiple * self::RATIO_H;    

    if($newWidth > $fitInsideWidth || $newHeight > $fitInsideHeight){
        echo " Tweak ";
        $ratioMultiple--;
        $this->tweakMultiplier($ratioMultiple, $fitInsideWidth, $fitInsideHeight);
    }else{
        return;
    }    
}

Answer 10

如果给出或不给出最大高度或宽度，使用@（jilles de wit）逻辑

注意事项：这些应该已经定义了！

$mh = given height limit; //optional
$mw = given width limit; //optional

$height = $nh =[your original height];
$width = $nw =[your original width];

守则

if($mh || $mw){
if(is_numeric($mh)){$h_fact = $mh / $nh;}
if(is_numeric($mw)){$v_fact = $mw / $nw;}

if(is_numeric($v_fact) && is_numeric($h_fact)  ){$im_fact = min($v_fact, $h_fact);}else{$im_fact=is_numeric($v_fact)?$v_fact:$h_fact;}
$nw = $nw * $im_fact;
$nh = $nh * $im_fact;
}

<强>重采样

$dst_img = imagecreatetruecolor($nw,$nh);
imagecopyresampled ($dst_img, $image, 0, 0, 0, 0, $nw, $nh, $width , $height);

Answer 11

class Image_Aspect_Ratio_Resize {
var $image_to_resize;
var $new_width;
var $new_height;
var $ratio;
var $new_image_name;
var $save_folder;

function resize() {
    if (!file_exists($this->image_to_resize)) {
        exit("File " . $this->image_to_resize . " does not exist.");
    }

    $info = GetImageSize($this->image_to_resize);

    if (empty($info)) {
        exit("The file " . $this->image_to_resize . " doesn't seem to be an image.");
    }

    $width = $info[0];
    $height = $info[1];
    $mime = $info['mime'];

    /* Keep Aspect Ratio? */

    if ($this->ratio) {
        $thumb = ($this->new_width < $width && $this->new_height < $height) ? true : false; // Thumbnail
        $bigger_image = ($this->new_width > $width || $this->new_height > $height) ? true : false; // Bigger Image

        if ($thumb) {
            if ($this->new_width >= $this->new_height) {
                $x = ($width / $this->new_width);

                $this->new_height = ($height / $x);
            } else if ($this->new_height >= $this->new_width) {
                $x = ($height / $this->new_height);

                $this->new_width = ($width / $x);
            }
        } else if ($bigger_image) {
            if ($this->new_width >= $width) {
                $x = ($this->new_width / $width);

                $this->new_height = ($height * $x);
            } else if ($this->new_height >= $height) {
                $x = ($this->new_height / $height);

                $this->new_width = ($width * $x);
            }
        }
    }


    $type = substr(strrchr($mime, '/'), 1);

    switch ($type) {
        case 'jpeg':
            $image_create_func = 'ImageCreateFromJPEG';
            $image_save_func = 'ImageJPEG';
            $new_image_ext = 'jpg';
            break;

        case 'png':
            $image_create_func = 'ImageCreateFromPNG';
            $image_save_func = 'ImagePNG';
            $new_image_ext = 'png';
            break;

        case 'bmp':
            $image_create_func = 'ImageCreateFromBMP';
            $image_save_func = 'ImageBMP';
            $new_image_ext = 'bmp';
            break;

        case 'gif':
            $image_create_func = 'ImageCreateFromGIF';
            $image_save_func = 'ImageGIF';
            $new_image_ext = 'gif';
            break;

        case 'vnd.wap.wbmp':
            $image_create_func = 'ImageCreateFromWBMP';
            $image_save_func = 'ImageWBMP';
            $new_image_ext = 'bmp';
            break;

        case 'xbm':
            $image_create_func = 'ImageCreateFromXBM';
            $image_save_func = 'ImageXBM';
            $new_image_ext = 'xbm';
            break;

        default:
            $image_create_func = 'ImageCreateFromJPEG';
            $image_save_func = 'ImageJPEG';
            $new_image_ext = 'jpg';
    }

    // New Image
    $image_c = ImageCreateTrueColor($this->new_width, $this->new_height);

    $new_image = $image_create_func($this->image_to_resize);

    ImageCopyResampled($image_c, $new_image, 0, 0, 0, 0, $this->new_width, $this->new_height, $width, $height);

    if ($this->save_folder) {
        if ($this->new_image_name) {
            $new_name = $this->new_image_name . '.' . $new_image_ext;
        } else {
            $new_name = $this->new_thumb_name(basename($this->image_to_resize)) . '_resized.' . $new_image_ext;
        }

        $save_path = $this->save_folder . $new_name;
    } else {
        /* Show the image without saving it to a folder */
        header("Content-Type: " . $mime);

        $image_save_func($image_c);

        $save_path = '';
    }

    $process = $image_save_func($image_c, $save_path);

    return array('result' => $process, 'new_file_path' => $save_path);
}}

/ *函数调用* /

$resize_image = new Image_Aspect_Ratio_Resize;
$new_width = (int) $_POST['new_width'];
$new_height = (int) $_POST['new_height'];
$resize_image->new_width = $new_width;
$resize_image->new_height = $new_height;
$resize_image->image_to_resize = $image; // Full Path to the file
$resize_image->ratio = true; // Keep aspect ratio
// Name of the new image (optional) - If it's not set a new will be added automatically
$resize_image->new_image_name = 'water_lilies_thumbnail';
/* Path where the new image should be saved. If it's not set the script will output the image without saving it */
$resize_image->save_folder = 'thumbs/';
$process = $resize_image->resize(); // Output image

Answer 12

这个怎么样：

double ratio = imageWidth/imageHeight;
int newHeight = Math.min(displayHeight, displayWidth / ratio); 
int newWidth =  Math.min(displayWidth, displayHeight * ratio);