Imagick::thumbnailImage

(PECL imagick 2, PECL imagick 3)

Imagick::thumbnailImage — 画像のサイズを変更する

説明

public Imagick::thumbnailImage(
    int $columns,
    int $rows,
    bool $bestfit = false,
    bool $fill = false,
    bool $legacy = false
): bool

画像のサイズを指定したものに変更し、関連付けられたプロパティをすべて削除します。ウェブ上での表示に適した小さなサムネイル画像を作成します。 3 番目のパラメータに true を指定すると、columns や rows にそれぞれの最大値を使用します。両方のパラメータが、マッチするまであるいは指定したパラメータより小さくなるまで縮小されます。

注意: パラメータ bestfit の挙動は Imagick 3.0.0 で変わりました。これより前のバージョンでは、200x150 の画像に対して 400x400 を指定した場合は何もせずそのままになっていました。 Imagick 3.0.0 以降では、この画像は 400x300 に拡大されます。これが、指定したサイズに対して「ベストフィット」する大きさだからです。 bestfit を使う場合は、幅と高さの両方を指定しなければなりません。

パラメータ

columns: 画像の幅。
rows: 画像の高さ。
bestfit: 最大値を強制的に使用するかどうか。

戻り値

成功した場合に true を返します。

エラー / 例外

エラー時に ImagickException をスローします。

例

例1 Imagick::thumbnailImage()

<?php
function thumbnailImage($imagePath) {
    $imagick = new \Imagick(realpath($imagePath));
    $imagick->setbackgroundcolor('rgb(64, 64, 64)');
    $imagick->thumbnailImage(100, 100, true, true);
    header("Content-Type: image/jpg");
    echo $imagick->getImageBlob();
}

?>

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User Contributed Notes 7 notes

down

Anonymous ¶

12 years ago

If the 3rd parameter is true, the image will be resized in such a way that it’ll be contained within the dimensions mentioned.
It’s like changing the dimensions of the image so that it can be contained in a box of given dimension.

Eg: Image’s dimension is 1600*800. If we use thumbnailImage(400, 400, true), the new image’s dimension will be 400*200.

Some of the previous notes in this page mentions that the image is resized proportionally so that its _smallest_ dimension matches the width or height specified, NOT both.
But this is not the case now. Both width & height of the image will be <= that mentioned in thumbnailImage().
Maybe imagick changed/updated the functionality.

down

jarrod at jarrodchristman dot com ¶

13 years ago

Even though thumbnailImage is meant to produce the smallest file size image possible, i found it didn't. I put together this code and bordering different compression settings, found it produced the smallest file size:

<?php
// Max vert or horiz resolution
$maxsize=550;

// create new Imagick object
$image = new Imagick('input_image_filename_and_location');

// Resizes to whichever is larger, width or height
if($image->getImageHeight() <= $image->getImageWidth())
{
// Resize image using the lanczos resampling algorithm based on width
$image->resizeImage($maxsize,0,Imagick::FILTER_LANCZOS,1);
}
else
{
// Resize image using the lanczos resampling algorithm based on height
$image->resizeImage(0,$maxsize,Imagick::FILTER_LANCZOS,1);
}

// Set to use jpeg compression
$image->setImageCompression(Imagick::COMPRESSION_JPEG);
// Set compression level (1 lowest quality, 100 highest quality)
$image->setImageCompressionQuality(75);
// Strip out unneeded meta data
$image->stripImage();
// Writes resultant image to output directory
$image->writeImage('output_image_filename_and_location');
// Destroys Imagick object, freeing allocated resources in the process
$image->destroy();

?>

I found setCompression to not function at all and had to use setImageCompression. The stripImage call is needed and strips out unneeded meta data. You can choose whatever filter you want, but i found lanczos to be the best for image reduction, though it is more computationally heavy.

down

web at johnbaldock dot com ¶

12 years ago

When shrinking a jpg you can get more then double the performance if you use <?php $image->setOption('jpeg:size', '800x532') ?>, exchanging 800x532 to the resolution you want the final image to be. For instance instead of this:

<?php
$image = new Imagick('foo.jpg');
?>

You would use this:

<?php
$image = new Imagick();
$image->setOption('jpeg:size', '800x532');
$image->readImage('foo.jpg');
?>

down

Anonymous ¶

16 years ago

Here is a function to calculate the new dimensions of a thumbnail, to fit within the given dimensions on both sides.

<?php
/**
 * Calculate new image dimensions to new constraints
 *
 * @param Original X size in pixels
 * @param Original Y size in pixels
 * @return New X maximum size in pixels
 * @return New Y maximum size in pixels
 */
function scaleImage($x,$y,$cx,$cy) {
    //Set the default NEW values to be the old, in case it doesn't even need scaling
    list($nx,$ny)=array($x,$y);
    
    //If image is generally smaller, don't even bother
    if ($x>=$cx || $y>=$cx) {
            
        //Work out ratios
        if ($x>0) $rx=$cx/$x;
        if ($y>0) $ry=$cy/$y;
        
        //Use the lowest ratio, to ensure we don't go over the wanted image size
        if ($rx>$ry) {
            $r=$ry;
        } else {
            $r=$rx;
        }
        
        //Calculate the new size based on the chosen ratio
        $nx=intval($x*$r);
        $ny=intval($y*$r);
    }    
    
    //Return the results
    return array($nx,$ny);
}
?>

Use it like this:

<?php
//Read original image and create Imagick object
$thumb=new Imagick($originalImageFilename);

//Work out new dimensions
list($newX,$newY)=scaleImage(
        $thumb->getImageWidth(),
        $thumb->getImageHeight(),
        $newMaximumWidth,
        $newMaximumHeight);

//Scale the image
$thumb->thumbnailImage($newX,$newY);

//Write the new image to a file
$thumb->writeImage($thumbnailFilename);
?>

down

-2

n-sw-bit at ya dot ru ¶

16 years ago

If you want to resize your picture to fit smallest parameter:

$fitbyWidth = (($maxWidth/$w)<($maxHeight/$h)) ?true:false;

if($fitbyWidth){
    $im->thumbnailImage($maxWidth, 0, false);
}else{
    $im->thumbnailImage(0, $maxHeight, false);
}

down

-1

raybdbomb . gmail ¶

17 years ago

As noted here
http://php.net/manual/en/ref.imagick.php
With either of the params as 0, the aspect ratio is maintained.

down

-4

sgarner at expio dot co dot nz ¶

17 years ago

With $fit == true, the image is resized proportionally so that its _smallest_ dimension matches the width or height specified, NOT both.

For example, if you say thumbnailImage(400, 400, true), on an image of 1600x800, it will be resized to 800x400, NOT 400x200 as you might expect.

The solution is to compare the original image's dimensions to the specified dimensions, and substitute zero for the smaller dimension, and set $fit = false.

i.e.: thumbnailImage(400, 0, false) would resize that 1600x800 image to 400x200.

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