PHP: imagerotate - Manual

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Last updated: Sat, 27 Jan 2007

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# imagerotate

(PHP 4 >= 4.3.0, PHP 5)

imagerotate -- Rotate an image with a given angle

## Описание

resource imagerotate ( resource source_image, float angle, int bgd_color [, int ignore_transparent] )

Rotates the `source_image` image using the given `angle` in degrees.

The center of rotation is the center of the image, and the rotated image is scaled down so that the whole rotated image fits in the destination image - the edges are not clipped.

## Список параметров

`source_image`

  The source image link

`angle`

  Rotation angle, in degrees.

`bgd_color`

  Specifies the color of the uncovered zone after the rotation

`ignore_transparent`

  If set and non-zero, transparent colors are ignored (otherwise kept).

## Возвращаемые значения

## Список изменений

Версия | Описание
--- | ---
5.1.0 | `ignore_transparent` was added.

## Примеры

Пример 1. Rotate an image 180 degrees

This example rotates an image 180 degrees - upside down.

`<?php
// File and rotation
$filename = 'test.jpg';
$degrees = 180;
// Content type
header('Content-type: image/jpeg');
// Load
$source = imagecreatefromjpeg($filename);
// Rotate
$rotate = imagerotate($source, $degrees, 0);
// Output
imagejpeg($rotate);
?>`

Результатом выполнения данного примера будет что-то подобное:

## Примечания

> Замечание: Эта функция доступна только в том случае, если PHP был скомпилирован со встроенной библиотекой GD.

add a note User Contributed Notes
imagerotate
Thomaschaaf
23-Feb-2007 07:21
`function rotate($degrees)
{
if(function_exists("imagerotate"))
$this->image = imagerotate($this->image, $degrees, 0);
else
{
function imagerotate($src_img, $angle)
{
$src_x = imagesx($src_img);
$src_y = imagesy($src_img);
if ($angle == 180)
{
$dest_x = $src_x;
$dest_y = $src_y;
}
elseif ($src_x <= $src_y)
{
$dest_x = $src_y;
$dest_y = $src_x;
}
elseif ($src_x >= $src_y)
{
$dest_x = $src_y;
$dest_y = $src_x;
}
$rotate=imagecreatetruecolor($dest_x,$dest_y);
imagealphablending($rotate, false);
switch ($angle)
{
case 270:
for ($y = 0; $y < ($src_y); $y++)
{
for ($x = 0; $x < ($src_x); $x++)
{
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $dest_x - $y - 1, $x, $color);
}
}
break;
case 90:
for ($y = 0; $y < ($src_y); $y++)
{
for ($x = 0; $x < ($src_x); $x++)
{
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $y, $dest_y - $x - 1, $color);
}
}
break;
case 180:
for ($y = 0; $y < ($src_y); $y++)
{
for ($x = 0; $x < ($src_x); $x++)
{
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $dest_x - $x - 1, $dest_y - $y - 1, $color);
}
}
break;
default: $rotate = $src_img;
};
return $rotate;
}
$this->image = imagerotate($this->image, $degrees);
}
}
This one works better than the one below from the 12th February and if the faster function is available it will take that.
It is still not optimized but turning pictures works better..`
crymsan
12-Feb-2007 02:44
`My php install does not have imagerotate (ubuntu). So, after fiddling with a few others I wrote my own code to rotate images in 90 degree increments. Any speed improvements would be great.
<?php
function imageRotate($src_img, $angle) {
$src_x = imagesx($src_img);
$src_y = imagesy($src_img);
if ($angle == 90 || $angle == -910) {
$dest_x = $src_y;
$dest_y = $src_x;
} else {
$dest_x = $src_x;
$dest_y = $src_y;
}
$rotate=imagecreatetruecolor($dest_x,$dest_y);
imagealphablending($rotate, false);
switch ($angle) {
case 90:
for ($y = 0; $y < ($src_y); $y++) {
for ($x = 0; $x < ($src_x); $x++) {
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $dest_x - $y - 1, $x, $color);
}
}
break;
case -90:
for ($y = 0; $y < ($src_y); $y++) {
for ($x = 0; $x < ($src_x); $x++) {
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $y, $dest_y - $x - 1, $color);
}
}
break;
case 180:
for ($y = 0; $y < ($src_y); $y++) {
for ($x = 0; $x < ($src_x); $x++) {
$color = imagecolorat($src_img, $x, $y);
imagesetpixel($rotate, $dest_x - $x - 1, $dest_y - $y - 1, $color);
}
}
break;
default: $rotate = $src_img;
};
return $rotate;
}
?>`
cedric dot francoys at easy-cms dot org
07-Jan-2007 10:26
`note for this message : "I was having a problem with rotating a PNG. I used -1 for ignore_transparent and in Firefox the uncovered area was transparent but in IE it showed as grey.
The real problem is IE 6.0 does not support transparent PNGs. So don't blame the imagerotatefunction. I don't know about IE 7 though."
In fact, IE6 doesn't handle the transparency for 24 bits PNG images. But it does for 8 bits PNG. (This problem has been solved with IE7).
Meanwhile, even if the input image is a 8 bits one, the image returned by imagesrotate is a 24 bit one ... so IE6 wont correctly display it.`
http://whitemarker.blogspot.com
03-Jan-2007 03:06
`I was having a problem with rotating a PNG. I used -1 for ignore_transparent and in Firefox the uncovered area was transparent but in IE it showed as grey.
The real problem is IE 6.0 does not support transparent PNGs. So don't blame the imagerotatefunction. I don't know about IE 7 though.`
m dot quinton at gmail dot com
14-Sep-2006 09:30
`with large file, where imagerotate is missing, you can use, when possible "convert" command from ImageMagick. Here is a sample script.
<?php
error_reporting(E_ALL);
header("Content-type: image/png");
$file = 'images/test/imgp2498.jpg';
image_rotate_with_convert($file, 90);
function image_rotate_with_convert($file, $angle){
passthru("convert -rotate $angle $file -");
}
?>`
barbarism at oscillatewildly dot com
17-Apr-2006 07:00
`If you pass "-1" into the last param of imagecreatefrompng, it preserves PNG transparently properly!
Exampe:
$filename = './documents/135.pdf.png';
$degrees = 40;
header('Content-type: image/png');
$source = imagecreatefrompng($filename);
$rotate = imagerotate($source, $degrees, -1);
imagealphablending($rotate, true);
imagesavealpha($rotate, true);
imagepng($rotate);`
Longhair
13-Apr-2006 02:03
`<?
//KOMPASS //PHP4.0 //GD2
$wert=0; //0-360 degree
$null=46; //Offset
$bgcolor=0x0033CC;
$grad=$wert+$null;
$kompass=imagecreatefromjpeg("bilder/kompass_ohne.jpg");
$nadel=imagecreatefromjpeg("bilder/nadel_bleu.jpg");
$mov_nadel= imagerotate($nadel, $grad, $bgcolor);
$xKom=imagesx($kompass);
$yKom=imagesy($kompass);
$x2Kom=$xKom/2;
$y2Kom=$yKom/2;
$xNad=imagesy($mov_nadel);
$yNad=imagesy($mov_nadel);
$y2Nad=$yNad/2+$x2Kom-$yNad; //92/2=46 + 100-92
$x2Nad=$xNad/2+$y2Kom-$xNad;
imagecopy ( $kompass, $mov_nadel, $x2Nad, $y2Nad, 0, 0, $xNad, $xNad );
header("Content-type: image/jpg");
//wird als JEPG-Bild Ausgegeben
//imagepng($kompass);
imagejpeg($kompass);
//imagegif($nadel);
imagedestroy($nadel);
imagedestroy($kompass);
?>`
gareth at crxchaos dot co dot uk
02-Mar-2006 07:19
`It's worth noting this function will only rotate true colour images - If you have a 256 colour pallet based image it will not rotate with this. Use the following code to convert the 256 colour image to truecolour first:
<?php
if (!imageistruecolor($im))
{
$w = imagesx($im);
$h = imagesy($im);
$t_im = imagecreatetruecolor($w,$h);
imagecopy($t_im,$im,0,0,0,0,$w,$h);
$im = $t_im;
}
?>
I have found no mention of this shortcoming of imagerotate anywhere on the Internet. Hopefully this will limit the number of people who, like me, are trying to troubleshoot a perfectly operation PHP install.`
olav-x at volvo-power.net
18-Nov-2005 04:17
`I tried the example provided by 'jonathan AT sharpmedia DOT net', and that gave me strange rotations, with offset on the image.
I dont need an advanced rotation script like that, so I used his function wrapper and make a more simple edition.
ps. the code above the function is only for test-purpose.
I'll retrieve srcpic from the db.
the idea here, is that I'll store rotated thumbs of the original thumb. Then the user can click on the thumb which is "correctly rotated" and then the original file will be rotated.
I think I'll make some backup function implemented too!
the idea is that the rotated files will have _ROT<int>.ext
eg. if you rotate the file "bicycle.jpg" 1 rotation (90 degrees), it will be copied to: bicycle_ROT1.jpg, 180 degrees would be _ROT2.jpg, and so on.
There is only 3 rots, I should have removed the ROT0 here, as well as the code might need improvement.
However, I think that simple codes like this ones, are the easiest ones to use as a foundation, as they are - simple!
What you can improve, if you want to do this:
* there is a lot! however, you have to wrap the $dst in something like:
if (!isset($dst)) {
}
eg. so you can over-ride the "save to", when calling the function!
this is beta 0.0000001 however, so play with it, slaughter it, whatever.
good luck!
Olav Alexander Mjelde
<?php
// #### start of test
$srcpic = 'bilder/biler/_tmp/foo.jpg';
echo rotateImage($srcpic, $dstpic, 1, 100);
echo rotateImage($srcpic, $dstpic, 2, 100);
echo rotateImage($srcpic, $dstpic, 3, 100);
// #### end of test
// this function rotates an image
function rotateImage($src, $dst, $count = 1, $quality = 95)
{
if (!file_exists($src)) {
return false;
}
// generate output filename
extension
$dst = substr($src, 0, strrpos($src, ".")) . "_ROT" . $count . substr($src, strrpos($src, "."), strlen($src));
switch ($count) {
case 0:
$degrees = 0;
break;
case 1:
$degrees = 90;
break;
case 2:
$degrees = 180;
break;
case 3:
$degrees = 270;
break;
}
// Load
$source = imagecreatefromjpeg($src);
// Rotate
$rotate = imagerotate($source, 360 - $degrees, 0);
// Output
imagejpeg($rotate, $dst, $quality);
imageDestroy($rotate);
imageDestroy($source);
return true;
}
?>`
simon_nuttall at hotmail dot com
27-Sep-2005 10:06
`The following is potentially useful. It extracts the central largest circle of an image into a square of specified size, and optionally rotates it. The rest of the square is made transparent, so useful for drawing over other images. I've named it after binocular effect because on some old TV shows whenever they show someone looking through binoculars the screen shows a big circular image with black edges.
<?php
function image_binocular_effect($src, $bearing, $out_square) {
// the source image is resampled to fit within the specified square, and rotated clockwise by bearing.
// the largest circle within the image is retained, the rest made transparent.
$out = imagecreatetruecolor($out_square, $out_square);
$width=imagesx($src);
$height=imagesy($src);
$square=min($width, $height);
imagecopyresampled($out, $src, 0, 0, ($width - $square)/2 , ($height - $square)/2, $out_square, $out_square, $square, $square);
$mask = imagecreatetruecolor($out_square, $out_square);
$black = ImageColorAllocate ($mask, 0, 0, 0);
$white = ImageColorAllocate ($mask, 255, 255, 255);
imagefilledrectangle($mask , 0, 0, $out_square, $out_square, $white);
$centrexy=$out_square / 2;
imagefilledellipse($mask, $centrexy, $centrexy, $out_square, $out_square, $black);
ImageColorTransparent($mask, $black);
imagecopymerge($out, $mask, 0, 0, 0, 0, $out_square, $out_square, 100);
if ($bearing != 0) {
$rotated_img=imagerotate($out , 360-$bearing, $white);
// take off only the rotated width
$rotated_map_width = imagesx($rotated_img);
$rotated_map_height = imagesy($rotated_img);
imagecopy($out, $rotated_img, 0, 0, ($rotated_map_width - $out_square) / 2, ($rotated_map_height - $out_square) / 2, $out_square, $out_square);
}
ImageColorTransparent($out, $white);
return $out;
}
// Create a sample image to demonstrate the effect, but looks much better on real photos.
$src = imagecreatetruecolor(200, 50);
imagefilledrectangle($src, 0, 0, 200, 50, imagecolorallocate($src, 255, 255, 255));
ImageString($src, 3, 10, 10, "This is a sample image to illustrate the binocular effect", imagecolorallocate($im, 192, 0, 0));
$img=image_binocular_effect($src, 72, 50);
ImagePNG($img,"test.png");
?>`
kumm at webstar dot hu
22-Aug-2005 12:59
`A better bugfix for jonathan AT sharpmedia DOT net's rotateImage function
you need to replace:
// Now copy tmp2 to $out;
imagecopy($out, $tmp2, 0, 0, ($angle == 270 ? abs($w - $h) : 0), 0, $h, $w);
with:
// Now copy tmp2 to $out;
if ($h>$w) {
imagecopy($out, $tmp2, 0, 0, 0, ($angle == 90 ? abs($w - $h) : 0), $h, $w);
} else {
imagecopy($out, $tmp2, 0, 0, ($angle == 270 ? abs($w - $h) : 0), 0, $h, $w);
}
otherwise the image gets moved when rotating a standing up image`
jmichel at faeryscape dot com
26-Apr-2005 11:56
`Imagerotate apparently destroy transparency information (transparent areas turn to black). For now the only walkaround I found is to use :
imagecolortransparent($image,imagecolorat($image,0,0));
but the result is quite awful if your original picture uses smooth transparency (which is probably the case with PNG pictures)`
oflashp at bk dot ru
22-Apr-2005 06:25
`standart code rotate image(only Jpeg)
<?
$r=0; //rotate
$img="254.jpg" //image
$source = imagecreatefromjpeg($img);
$img = imagerotate($source, $r, 0);
imagejpeg($img);
?>`
11-Apr-2005 09:58
`Just an advice for those who want to create image galleries and want to add a function to rotate pictures.
The way this here works is always to decompress the picture, rotate it and compress it again.
Therefore there _WILL_ always be a loss in quality. The more often you rotate the image the stronger the artefacts will be visible.
Also using ImageMagick, if available does not help, as it also does not support lossless JPG manipulations.
If you need a rotate function, ask your provider to install JPEGTRAN on the machine your server runs on and use the command line tool from your php application.`
wulff at fyens dot dk
01-Mar-2005 01:22
`I liked the rotateImageBicubic function implemented by darren at lucidtone dot com. But it just snipped off the parts of the image that were outside the original image.
I fixed this, even though I admit that my solution is a bit naive. But it might come in handy for somebody.
Also his bicubic implementation was broken on my machine so I left it out, if you need it just copy and paste it from above.
<?php
// $src_img - a GD image resource
// $angle - degrees to rotate clockwise, in degrees
// returns a GD image resource
// USAGE:
// $im = imagecreatefrompng('test.png');
// $im = imagerotate($im, 15);
// header('Content-type: image/png');
// imagepng($im);
function imageRotate($src_img, $angle, $bicubic=false) {
// convert degrees to radians
$angle = $angle + 180;
$angle = deg2rad($angle);
$src_x = imagesx($src_img);
$src_y = imagesy($src_img);
$center_x = floor($src_x/2);
$center_y = floor($src_y/2);
$cosangle = cos($angle);
$sinangle = sin($angle);
$corners=array(array(0,0), array($src_x,0), array($src_x,$src_y), array(0,$src_y));
foreach($corners as $key=>$value) {
$value[0]-=$center_x; //Translate coords to center for rotation
$value[1]-=$center_y;
$temp=array();
$temp[0]=$value[0]*$cosangle+$value[1]*$sinangle;
$temp[1]=$value[1]*$cosangle-$value[0]*$sinangle;
$corners[$key]=$temp;
}
$min_x=1000000000000000;
$max_x=-1000000000000000;
$min_y=1000000000000000;
$max_y=-1000000000000000;
foreach($corners as $key => $value) {
if($value[0]<$min_x)
$min_x=$value[0];
if($value[0]>$max_x)
$max_x=$value[0];
if($value[1]<$min_y)
$min_y=$value[1];
if($value[1]>$max_y)
$max_y=$value[1];
}
$rotate_width=round($max_x-$min_x);
$rotate_height=round($max_y-$min_y);
$rotate=imagecreatetruecolor($rotate_width,$rotate_height);
imagealphablending($rotate, false);
imagesavealpha($rotate, true);
//Reset center to center of our image
$newcenter_x = ($rotate_width)/2;
$newcenter_y = ($rotate_height)/2;
for ($y = 0; $y < ($rotate_height); $y++) {
for ($x = 0; $x < ($rotate_width); $x++) {
// rotate...
$old_x = round((($newcenter_x-$x) * $cosangle + ($newcenter_y-$y) * $sinangle))
+ $center_x;
$old_y = round((($newcenter_y-$y) * $cosangle - ($newcenter_x-$x) * $sinangle))
+ $center_y;
if ( $old_x >= 0 && $old_x < $src_x
&& $old_y >= 0 && $old_y < $src_y ) {
$color = imagecolorat($src_img, $old_x, $old_y);
} else {
// this line sets the background colour
$color = imagecolorallocatealpha($src_img, 255, 255, 255, 127);
}
imagesetpixel($rotate, $x, $y, $color);
}
}
return($rotate);
}
?>`
jonathan AT sharpmedia DOT net
17-Feb-2005 10:28
`This method rotates an image in 90 degree increments (eg count should be between 1 and 3) and avoids the problems of image scaling that imageRotate has...
<?php
function rotateImage($src, $count = 1, $quality = 95)
{
if (!file_exists($src)) {
return false;
}
list($w, $h) = getimagesize($src);
if (($in = imageCreateFromJpeg($src)) === false) {
echo "Failed create from source<br>";
return false;
}
$angle = 360 - ((($count > 0 && $count < 4) ? $count : 0 ) * 90);
if ($w == $h || $angle == 180) {
$out = imageRotate($in, $angle, 0);
} elseif ($angle == 90 || $angle == 270) {
$size = ($w > $h ? $w : $h);
// Create a square image the size of the largest side of our src image
if (($tmp = imageCreateTrueColor($size, $size)) == false) {
echo "Failed create square trueColor<br>";
return false;
}
// Exchange sides
if (($out = imageCreateTrueColor($h, $w)) == false) {
echo "Failed create trueColor<br>";
return false;
}
// Now copy our src image to tmp where we will rotate and then copy that to $out
imageCopy($tmp, $in, 0, 0, 0, 0, $w, $h);
$tmp2 = imageRotate($tmp, $angle, 0);
// Now copy tmp2 to $out;
imageCopy($out, $tmp2, 0, 0, ($angle == 270 ? abs($w - $h) : 0), 0, $h, $w);
imageDestroy($tmp);
imageDestroy($tmp2);
} elseif ($angle == 360) {
imageDestroy($in);
return true;
}
imageJpeg($out, $src, $quality);
imageDestroy($in);
imageDestroy($out);
return true;
}
?>`
Borszczuk
05-Jan-2005 05:21
`Here's a function that implements right angle (multiplicity of 90 degs - 90, 180, 270) rotation if you need one but lacks native imagerotate() or you don't want non-square images to be scaled down as with imagerotate(). As you probably noticed it's not self contained function, as 180 rotation is handled by ImageFlip() function to gain the performance. The ImageFlip() function used is published here: http://php.net/imagecopy in the comment of mine placed on 05-Jan-2005 04:30
Please note: that in case of 0 degrees rotation handle to imgSrc is returned which may lead to problems if you imagedestroy() it undonditionaly. To solve that you shall add imagecopy($imgDest, $imgSrc, 0,0, 0,0,$srcX, $srcY) in proper place which I have intentionally ommited to save memory resources
<?php
// $imgSrc - GD image handle of source image
// $angle - angle of rotation. Needs to be positive integer
// angle shall be 0,90,180,270, but if you give other it
// will be rouned to nearest right angle (i.e. 52->90 degs,
// 96->90 degs)
// returns GD image handle of rotated image.
function ImageRotateRightAngle( $imgSrc, $angle )
{
// ensuring we got really RightAngle (if not we choose the closest one)
$angle = min( ( (int)(($angle+45) / 90) * 90), 270 );
// no need to fight
if( $angle == 0 )
return( $imgSrc );
// dimenstion of source image
$srcX = imagesx( $imgSrc );
$srcY = imagesy( $imgSrc );
switch( $angle )
{
case 90:
$imgDest = imagecreatetruecolor( $srcY, $srcX );
for( $x=0; $x<$srcX; $x++ )
for( $y=0; $y<$srcY; $y++ )
imagecopy($imgDest, $imgSrc, $srcY-$y-1, $x, $x, $y, 1, 1);
break;
case 180:
$imgDest = ImageFlip( $imgSrc, IMAGE_FLIP_BOTH );
break;
case 270:
$imgDest = imagecreatetruecolor( $srcY, $srcX );
for( $x=0; $x<$srcX; $x++ )
for( $y=0; $y<$srcY; $y++ )
imagecopy($imgDest, $imgSrc, $y, $srcX-$x-1, $x, $y, 1, 1);
break;
}
return( $imgDest );
}
?>`
darren at lucidtone dot com
07-Dec-2004 08:43
`Here's a neat function for those of us who don't have imagerotate() on our servers. It's based on a comment from ron at korving dot demon dot nl on the manual page for imagecopyresampled.
I'm still not 100% on coping with transparency, but this function seems to cope okay. It doesn't resize to fit within bounds, it just rotates and you lose anything outside the image box.
The bicubic mode is slooow.
If you want to be able to change the background colour, pass in a colour and use it where indicated. The line I used just sets it transparent.
<?
// $src_img - a GD image resource
// $angle - degrees to rotate clockwise, in degrees
// returns a GD image resource
// USAGE:
// $im = imagecreatefrompng('test.png');
// $im = imagerotate($im, 15);
// header('Content-type: image/png');
// imagepng($im);
function imageRotateBicubic($src_img, $angle, $bicubic=false) {
// convert degrees to radians
$angle = $angle + 180;
$angle = deg2rad($angle);
$src_x = imagesx($src_img);
$src_y = imagesy($src_img);
$center_x = floor($src_x/2);
$center_y = floor($src_y/2);
$rotate = imagecreatetruecolor($src_x, $src_y);
imagealphablending($rotate, false);
imagesavealpha($rotate, true);
$cosangle = cos($angle);
$sinangle = sin($angle);
for ($y = 0; $y < $src_y; $y++) {
for ($x = 0; $x < $src_x; $x++) {
// rotate...
$old_x = (($center_x-$x) * $cosangle + ($center_y-$y) * $sinangle)
+ $center_x;
$old_y = (($center_y-$y) * $cosangle - ($center_x-$x) * $sinangle)
+ $center_y;
if ( $old_x >= 0 && $old_x < $src_x
&& $old_y >= 0 && $old_y < $src_y ) {
if ($bicubic == true) {
$sY = $old_y + 1;
$siY = $old_y;
$siY2 = $old_y - 1;
$sX = $old_x + 1;
$siX = $old_x;
$siX2 = $old_x - 1;
$c1 = imagecolorsforindex($src_img, imagecolorat($src_img, $siX, $siY2));
$c2 = imagecolorsforindex($src_img, imagecolorat($src_img, $siX, $siY));
$c3 = imagecolorsforindex($src_img, imagecolorat($src_img, $siX2, $siY2));
$c4 = imagecolorsforindex($src_img, imagecolorat($src_img, $siX2, $siY));
$r = ($c1['red'] + $c2['red'] + $c3['red'] + $c4['red'] ) << 14;
$g = ($c1['green'] + $c2['green'] + $c3['green'] + $c4['green']) << 6;
$b = ($c1['blue'] + $c2['blue'] + $c3['blue'] + $c4['blue'] ) >> 2;
$a = ($c1['alpha'] + $c2['alpha'] + $c3['alpha'] + $c4['alpha'] ) >> 2;
$color = imagecolorallocatealpha($src_img, $r,$g,$b,$a);
} else {
$color = imagecolorat($src_img, $old_x, $old_y);
}
} else {
// this line sets the background colour
$color = imagecolorallocatealpha($src_img, 255, 255, 255, 127);
}
imagesetpixel($rotate, $x, $y, $color);
}
}
return $rotate;
}
?>`
jon at driestone dot com
07-Oct-2004 08:42
`imagerotate does not preserve the alpha channel, so if you want to rotate a PNG you need to get
creative. I don't see any command to retrieve the alpha information from an image (as far as
I could see,) so you'll have to do a bit of manual labor before hand. In my case I created a
second PNG file with the alpha saved as RGB data and manually "copied" the data from source
to destination:
function alpha_rotate($dst,$src,$rotate,$offsetX,$offsetY){
$top = imagecreatefrompng("image_processing/shadow.png");
$top_alpha = imagecreatefrompng("image_processing/shadow_alpha.png");
imagecopyresampled($top,$src,0,0,0,0,100,100,100,100);
$top = imagerotate($top,$rotate,0x000000);
$top_alpha = imagerotate($top_alpha,$rotate,0x000000);
for ($theX=0;$theX<imagesx($top);$theX++){
for ($theY=0;$theY<imagesy($top);$theY++){
$rgb = imagecolorat($top,$theX,$theY);
$r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
$rgb = imagecolorat($top_alpha,$theX,$theY);
$a = $rgb & 0xFF;
$a = 127-floor($a/2);
$myColor = imagecolorallocatealpha($top,$r,$g,$b,$a);
imagesetpixel($dst,($theX+$offsetX),($theY+$offsetY),$myColor);
}
}
}`
christoph (at) raketenbasis (dot) de
04-Oct-2004 12:41
`The default direction of imageRotate() is counter clockwise. Heres a little function which solves the problem.
<?php
function rotate(&$image_source, $rotate_value, $rotate_clockwise = true) {
if($rotate_clockwise == true) {
$rotate_value = 360 - $rotate_value;
}
$image_source = imageRotate($image_source, $rotate_value, 0);
}
?>`
add a note
imagesavealpha imagerectangle

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