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imagepng

(PHP 4, PHP 5, PHP 7, PHP 8)

imagepng — PNG イメージをブラウザまたはファイルに出力する

説明

imagepng(
    GdImage $image,
    resource|string|null $file = null,
    int $quality = -1,
    int $filters = -1
): bool

指定した image から、PNG 画像を出力あるいは保存します。

パラメータ

image: imagecreatetruecolor()のような画像作成関数が返す GdImage オブジェクト。
file: ファイル保存先のパスあるいはオープン中のリソース (この関数が値を戻した後で自動的にクローズされます)。省略したり null を設定したりした場合は、画像ストリームを直接出力します。

注意:
quality および filters を使用しない場合は、 null を指定することはできません。
quality: 圧縮レベル。0 (圧縮しない) から 9 までの値です。デフォルト (-1) は、zlib の圧縮レベルのデフォルトを使います。詳細は、» zlib マニュアルをご覧ください。
filters: PNG ファイルの大きさを小さくします。これはビットマスクフィールドで、定数 PNG_FILTER_* の組み合わせを指定します。 PNG_NO_FILTER や PNG_ALL_FILTERS を使用すると、全フィルタを一括で無効にしたり有効にしたりできます。デフォルト値 (-1) は、フィルタリングを無効にします。

警告
システムにインストールされた libgd は、filters パラメータを無視します。

戻り値

成功した場合に true を、失敗した場合に false を返します。

警告

しかしながら、libgd がイメージの出力に失敗した場合、この関数は true を返します。

エラー / 例外

quality が不正の場合、 ValueError をスローします。

変更履歴

バージョン	説明
8.4.0	`quality` が不正の場合、 ValueError をスローするようになりました。
8.0.0	`image` は、 GdImage クラスのインスタンスを期待するようになりました。これより前のバージョンでは、有効な `gd` resource が期待されていました。

例

<?php
$im = imagecreatefrompng("test.png");

header('Content-Type: image/png');

imagepng($im);
imagedestroy($im);
?>

参考

imagegif() - 画像をブラウザあるいはファイルに出力する
imagewbmp() - 画像をブラウザあるいはファイルに出力する
imagejpeg() - 画像をブラウザあるいはファイルに出力する
imagetypes() - この PHP がサポートしている画像形式を返す
imagesavealpha() - 画像を保存する際に、完全なアルファチャネル情報を保存するかどうかを指定する

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User Contributed Notes 33 notes

down

matteosistisette at gmail dot com ¶

13 years ago

The name "quality" for the compression parameter is quite misleading, as png compression is always lossless. The trade off is between speed and filesize, it cannot affect quality.

Here's something I found at stackoverflow; I haven't checked it, but if it is correct it should definitely included in the documentation:

---
from php source (gd.h):

/* 2.0.12: Compression level: 0-9 or -1, where 0 is NO COMPRESSION at all,
* 1 is FASTEST but produces larger files, 9 provides the best
* compression (smallest files) but takes a long time to compress, and
* -1 selects the default compiled into the zlib library.
*/
Conclusion: Based on the Zlib manual (http://www.zlib.net/manual.html) the default compression level is set to 6.
---

Regarding suggestions to rescale the 0-99 quality range of jpeg into the 0-9 range of png, note that for jpeg 99 is minimum compression (maximum quality) while for png 9 is maximum compression (quality doesn't change).

down

Anonymous ¶

21 years ago

"Tip: As with anything that outputs its result directly to the browser, you can use the output-control functions (http://www.php.net/manual/en/ref.outcontrol.php) to capture the output of this function, and save it in a string (for example)."

ob_start();
imagepng($image);
$image_data = ob_get_contents();
ob_end_clean();

And now you can save $image_data to a database, for example, instead of first writing it to file and then reading the data from it. Just don't forget to use mysql_escape_string...

down

mail at stefanbechtold dot de ¶

21 years ago

to all the ones, who like having their users fill their profil with an image without destroying a fixed design the following should be a great way to handle this problem.

this file opens a picture from $imagepath and returns it as a valid picture to embed in: <img src="file.php?image=123.jpg[?maxX=200&maxY=150]"> (in [] = optional)

but this file does more than this. it also adds black borders to files that are smaller than the max. size, so adding borders to the left and right where a image is too high :-)

if there is a need for a copyright note this script will also help you. you can put in a various text to $copyright. the text length should be in relationship to $maxX and $maxY.

Well there are other features of the script, just try'em out and have fun with it :-)

bye 

<?php

# standard height & weight if not given
if(!isset($maxX)) $maxX = 100;
if(!isset($maxY)) $maxY = 75;

# colour- & textvalues
$picBG = "0,0,0"; # RGB-value !
$picFG = "104,104,104"; # RGB-value !
$copyright = "stefan bechtold"; 
$font = 1;

# minimal & maximum zoom
$minZoom = 1; # per cent related on orginal (!=0)
$maxZoom = 200; # per cent related on orginal (!=0)

# paths
$imgpath = "userimages/"; # ending with "/" !
$nopicurl = "../images/nopic.jpg"; # starting in $imagepath!!!
$nofileurl = "../images/nofile.jpg"; # starting in $imagepath!!!

if(!isset($image) || empty($image))
    $imageurl = $imgpath . $nopicurl;
elseif(! file_exists($imgpath . trim($image)))
    $imageurl = $imgpath . $nofileurl;
else
    $imageurl = $imgpath . trim($image);

# reading image
$image = getImageSize($imageurl, $info); # $info, only to handle problems with earlier php versions...
switch($image[2]) {
      case 1:
       # GIF image
        $timg = imageCreateFromGIF($imageurl);
        break;
    case 2:
       # JPEG image
        $timg = imageCreateFromJPEG($imageurl);
        break;
    case 3:
       # PNG image
        $timg = imageCreateFromPNG($imageurl);
        break;
}

# reading image sizes
$imgX = $image[0];
$imgY = $image[1];

# calculation zoom factor 
$_X = $imgX/$maxX * 100;
$_Y = $imgY/$maxY * 100;

# selecting correct zoom factor, so that the image always keeps in the given format
# no matter if it is more higher than wider or the other way around
if((100-$_X) < (100-$_Y)) $_K = $_X;
else $_K = $_Y;

# zoom check to the original
if($_K > 10000/$minZoom) $_K = 10000/$minZoom;
if($_K < 10000/$maxZoom) $_K = 10000/$maxZoom;

# calculate new image sizes
$newX = $imgX/$_K * 100;
$newY = $imgY/$_K * 100;

# set start positoin of the image
# always centered 
$posX = ($maxX-$newX) / 2;
$posY = ($maxY-$newY) / 2;

# creating new image with given sizes
$imgh = imageCreateTrueColor($maxX, $maxY);

# setting colours
$cols = explode(",", $picBG);
$bgcol = imageColorallocate($imgh, trim($cols[0]), trim($cols[1]), trim($cols[2]));
$cols = explode(",", $picFG);
$fgcol = imageColorallocate($imgh, trim($cols[0]), trim($cols[1]), trim($cols[2]));

# fill background
imageFill($imgh, 0, 0, $bgcol);

# create small copy of the image
imageCopyResampled($imgh, $timg, $posX, $posY, 0, 0, $newX, $newY, $image[0], $image[1]);

# writing copyright note
imageStringUp($imgh, $font, $maxX-9, $maxY-3, $copyright, $fgcol);

# output
switch($image[2]) {
      case 1:
    # GIF image
        header("Content-type: image/gif");
        imageGIF($imgh);
    case 2:
    # JPEG image
        header("Content-type: image/jpeg");
        imageJPEG($imgh);
    case 3:
    # PNG image
        header("Content-type: image/png");
        imagePNG($imgh);
}

# cleaning cache
imageDestroy($timg);
imageDestroy($imgh);

?>

down

luxian.m [at] gmail [dot] com ¶

16 years ago

If you want to open a png image with alpha blending, you need to do something like this:

<?php
$file = 'semitransparent.png'; // path to png image
$img = imagecreatefrompng($file); // open image
imagealphablending($img, true); // setting alpha blending on
imagesavealpha($img, true); // save alphablending setting (important)
?>

I spent almost a day to find out why alpha blending doesn't work. I hope this is usefull to others too :)

down

r.lomas at infonie.fr ¶

14 years ago

I just lost about 4 hours on a really stupid problem. My images on the local server were somehow broken and therefore did not display in the browsers. After much looking around and testing, including re-installing apache on my computer a couple of times, I traced the problem to an included file. 
No the problem was not a whitespace, but the UTF BOM encoding character at the begining of one of my inluded files...
So beware of your included files!
Make sure they are not encoded in UTF or otherwise in UTF without BOM.
Hope it save someone's time.

down

geompse at gmail dot com ¶

12 years ago

Be careful when using a variable for the file name.
PHP behavior with $filename differs when switching to PHP5.4 : PHP5.3 will use $filename='' the same way as $filename=NULL (e.g. no warning)
<?php
$im = imagecreatetruecolor(10,10);
imagepng($im,'',9); # Warning: imagepng(): Filename cannot be empty
imagepng($im,NULL,9); # works as expected
imagedestroy($im);
?>

down

johnbeech at mkv25.net ¶

21 years ago

PNG files are already compressed. They use a lossless compression algorithm. If you are using HighColour images, the compression only does so much. For low colour images (16 or 256) the compression is much better.

It is pointless trying to compress the images further before sending to a browser.

down

mhorne69 at gmail dot com ¶

14 years ago

If you're generating an image dynamically based on post data and don't want to save it to the server, sending it to be displayed can cause problems as when the person tries to save it, the browser will request it again from the server (causing any post data to be lost and probably a corrupted png).



The easiest way to get around this is to force it to download using the content disposition header, for example:



<?php

header('Content-Disposition: Attachment;filename=image.png');

header('Content-type: image/png');

?>

down

Chris F ¶

9 years ago

I was curious about the relationship between quality, processing time and resulting image size, so I created this little benchmark to test it (The image used was originally RGB_24bits_palette_R85.png, found on wikipedia). Results are at the bottom.
<?php
$sizes = ['32', '64', '128', '256', '512', '1024', '2048'];

foreach ($sizes as $size) {
    echo "\nSize: {$size}x{$size}px:\n";

    $image = imagecreatefrompng("images/test{$size}.png");
    for ($quality = 0; $quality < 10; $quality++) {
        ob_start();

        $start = microtime(true);
        imagepng($image, null, $quality);
        $elapsed = microtime(true) - $start;

        $blob = ob_get_contents();
        ob_end_clean();

        $blobSize = strlen($blob);
        echo "quality: $quality, size: $blobSize, elapsed: $elapsed\n";
    }

    imagedestroy($image);
}

// Results (some omitted for brevity):

// Size: 32x32px:
// quality: 0, size: 3172, elapsed: 0.00013399124145508
// quality: 1, size: 266, elapsed: 9.4890594482422E-5
// quality: 2, size: 264, elapsed: 7.7009201049805E-5
// quality: 3, size: 223, elapsed: 7.4863433837891E-5
// quality: 4, size: 225, elapsed: 8.5830688476562E-5
// quality: 5, size: 209, elapsed: 8.5115432739258E-5
// quality: 6, size: 208, elapsed: 9.608268737793E-5
// quality: 7, size: 205, elapsed: 0.0001060962677002
// quality: 8, size: 186, elapsed: 0.00015091896057129
// quality: 9, size: 181, elapsed: 0.00022006034851074

// Size: 128x128px:
// quality: 0, size: 49425, elapsed: 0.0010969638824463
// quality: 1, size: 976, elapsed: 0.00091886520385742
// quality: 2, size: 938, elapsed: 0.00088310241699219
// quality: 3, size: 925, elapsed: 0.00087594985961914
// quality: 4, size: 608, elapsed: 0.0009760856628418
// quality: 5, size: 607, elapsed: 0.00098395347595215
// quality: 6, size: 601, elapsed: 0.0010099411010742
// quality: 7, size: 602, elapsed: 0.001086950302124
// quality: 8, size: 521, elapsed: 0.001910924911499
// quality: 9, size: 491, elapsed: 0.0029060840606689

// Size: 512x512px:
// quality: 0, size: 788279, elapsed: 0.012928009033203
// quality: 1, size: 12467, elapsed: 0.013065099716187
// quality: 2, size: 11885, elapsed: 0.013008117675781
// quality: 3, size: 11190, elapsed: 0.013030052185059
// quality: 4, size: 7311, elapsed: 0.016619920730591
// quality: 5, size: 6994, elapsed: 0.016351222991943
// quality: 6, size: 6475, elapsed: 0.016234159469604
// quality: 7, size: 6432, elapsed: 0.016525983810425
// quality: 8, size: 6094, elapsed: 0.022937774658203
// quality: 9, size: 5649, elapsed: 0.065664052963257

// Size: 2048x2048px:
// quality: 0, size: 12605375, elapsed: 0.20983290672302
// quality: 1, size: 451735, elapsed: 0.19678711891174
// quality: 2, size: 409375, elapsed: 0.19415307044983
// quality: 3, size: 366404, elapsed: 0.20460414886475
// quality: 4, size: 312538, elapsed: 0.22785305976868
// quality: 5, size: 281671, elapsed: 0.23320484161377
// quality: 6, size: 244248, elapsed: 0.28935289382935
// quality: 7, size: 238310, elapsed: 0.33481192588806
// quality: 8, size: 217038, elapsed: 0.71698379516602
// quality: 9, size: 208881, elapsed: 1.858146905899
?>

down

bgd1977 at hotmail dot com ¶

22 years ago

I have experienced segfaults and bus errors with the following configuration: FreeBSD4.4, Apache 1.3.26, PHP 4.2.2, GD-1.8.4, PDFlib 4.0.1. The apache process crashed when calling the imagepng function, but it didn't crash when calling the imagejpg function, or imagecreatefrompng...

 Some wasted hours (lots) later, in which I have tried to recompile gd, libpng, php, libjpeg, what-not, I have found the following advices:
http://bugs.php.net/bug.php?id=16841

 So the problem was not with the png library, but rather with the PDFlib. Even though all the threads led to a png-problem... so I have simply upgraded to PDFlib 4.0.3 (w/o any special configure arguments; --with-libpng didn't work anyways), recompiled PHP, and now everything works (imagepng, pdf creation, etc.).

 Hope this helps,
 bogdan

down

php dot net at phor dot net ¶

11 years ago

If you are outputting a PNG directly in response to a client request it is important to check your web server configuration.

Some clients may request your images with a <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html">accept header</a> of image/*. Default configurations of Apache and possibly other servers will by default NOT allow your script to run in response to this request.

Apache is specifically discussed at http://stackoverflow.com/q/19169337 but other server have been documented to have issue too.

In other words, when testing your application don't just use the web browser, consider a phone's browser and networking libraries which could send different headers.

down

adrenalin at NOSPAM dot myrealbox dot com ¶

18 years ago

Trying to resize a png 256 colors image and save it in 256 colors with a correct color palette ? (if you'll save a 256 color image in truecolor palette the result image will have a big size).
I spent some hours trying various function to get a good quality 256 color png image, but because of color palette the result image quality was awful.
But thank to the comment of zmorris at zsculpt dot com from imagetruecolortopalette function page, i figured out how to get a properly image!

<?php
function resize_png($src,$dst,$dstw,$dsth) {
    list($width, $height, $type, $attr) = getimagesize($src);
    $im = imagecreatefrompng($src);
    $tim = imagecreatetruecolor($dstw,$dsth);
    imagecopyresampled($tim,$im,0,0,0,0,$dstw,$dsth,$width,$height);
    $tim = ImageTrueColorToPalette2($tim,false,255);
    imagepng($tim,$dst);
}
//zmorris at zsculpt dot com function, a bit completed
function ImageTrueColorToPalette2($image, $dither, $ncolors) {
    $width = imagesx( $image );
    $height = imagesy( $image );
    $colors_handle = ImageCreateTrueColor( $width, $height );
    ImageCopyMerge( $colors_handle, $image, 0, 0, 0, 0, $width, $height, 100 );
    ImageTrueColorToPalette( $image, $dither, $ncolors );
    ImageColorMatch( $colors_handle, $image );
    ImageDestroy($colors_handle);
    return $image;
}
?>

Good luck,
Namolovan Nicolae, Moldova

down

alex at gateway-productions dot com ¶

17 years ago

barts code below does not work at least with gd 2

Only returns a blank image with alpha not the source resized

        $im = ImageCreateFromPNG($sourcefile);
        $im_dest = imagecreatetruecolor ($forcedwidth, $forcedheight);
        imagealphablending($im_dest, false);
        imagecopyresampled($im_dest, $im, 0, 0, 0, 0, $wm_width, $wm_height, $forcedwidth, $forcedheight);
        imagesavealpha($im_dest, true);
        imagepng($im_dest, $destfile);
        imagedestroy($img_dest);

ps you also forgot image destroy and you had a random var in imagepng undefined in your post

down

wietse89 at gmail dot com ¶

14 years ago

When you allow multiple output formats, (jpg/png) but want to use the 1-100 quality scale (like jpg), you will have to format the number:

<?php
$pngQuality = ($quality - 100) / 11.111111;
$pngQuality = round(abs($pngQuality));
imagepng($resource, $path, $pngQuality);
?>

down

neburk0rk at gmail dot com ¶

19 years ago

This is my way to store PNG-images in a MySQL database... You cannot directly store the PNG-image in a variable, and then parse it in the database, cos if you try to define it to a variable, it'll still just output it...
In my method i use three functions
 to "capture" the output and store it in a variable; ob_start (to start the output buffering),    ob_get_contents  (to capture the output),    and  ob_end_clean (to erase the cache, and end the output buffering)

<?php
$imagefile = "changethistogourimage.gif";

$image = imagecreatefromgif($imagefile);
ob_start();
imagepng($image);
$imagevariable = ob_get_contents();
ob_end_clean();

/*
HERE YOU CAN MESS WITH THE $imagevariable AS YOU LIKE
*/
?>

down

Messerli at messerli dot net ¶

1 year ago

// Send the Image as Base64 Data directly to the browser.
// No File on the Server! No Hacker Problem. 

  ob_start();
  imagepng($img);
  $ImageData=ob_get_contents();
  ob_end_clean();
  echo '<img src="data:image/jpg;base64,'.base64_encode($ImageData).'">';

down

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PHPのお勉強！

imagepng

説明

パラメータ

戻り値

エラー / 例外

変更履歴

例

参考

Found A Problem?

User Contributed Notes 33 notes