Creating PNG thumbnail using PHP

问题

I'm trying to create a thumbnail image it returned an error, that imagecopyresized() expects 2 parameter to be resource, but it can create the image but the output is only a small black image.

here is my code

$image = "asd.PNG";

$image_size = getimagesize($image);
$image_width = $image_size[0]; 
$image_height = $image_size[1];


$new_size = ($image_width + $image_height)/($image_width*($image_height/45));

$new_width = $image_width * $new_size;

$new_height = $image_height * $new_size;

$new_image = imagecreatetruecolor($new_width, $new_height);

$old_mage = imagecreatefrompng($image); 

imagecopyresized($new_image, $image, 0, 0, 0, 0, $new_width, $new_height, $image_width, $image_height);

imagepng($new_image, $image.'.thumb.png');

回答1:

Here's one function that does it. Uses assist function for PNG transparency.

public function redimesionImage($endThu,$newX,$newY,$endImg,$fileType){

    // Copy the image to be resized
    copy($endThu, $endImg);

    // Retrieves the image data
    list($width, $height) = getimagesize($endImg);

    // If the width is greater ...
    if($width >= $height) {

        // I set the width of the image to the desired size ...
        $newXimage = $newX;

        // And calculate the size of the time to not stretch the image
        $newYimage = ($height / $width) * $newXimage;

    } else {

        // Define the desired height ...
        $newYimage = $newY;

        // And calculate the width to not stretch the image
        $newXimage = ($width / $height) * $newYimage;
    }

    // Creates an initial image in memory with calculated measures
    $imageInicial = imagecreatetruecolor(ceil($newXimage), ceil($newYimage));

    // I check the extension of the image and create their respective image
    if ($fileType == 'jpeg')   $endereco = imagecreatefromjpeg($endImg);
    if ($fileType == 'jpg')  $endereco = imagecreatefromjpeg($endImg);      
    if ($fileType == 'png')    {
        $endereco = imagecreatefrompng($endImg);
        imagealphablending($imageInicial, false);
        imagesavealpha($imageInicial,true);
        $transparent = imagecolorallocatealpha($imageInicial, 255, 255, 255, 127);
        imagefilledrectangle($endereco, 0, 0, $newXimage, $newYimage, $transparent);
    }
    if ($fileType == 'gif')  {
        $endereco = imagecreatefromgif($endImg);
        $this->setTransparency($imageInicial,$endereco);
    }

    // I merge the image to be resized with created in memory
    imagecopyresampled($imageInicial, $endereco, 0, 0, 0, 0, ceil($newXimage), ceil($newYimage), ceil($width), ceil($height));

    // Creates the image in its final lacal, according to its extension
    if ($fileType == 'jpeg') imagejpeg($imageInicial, $endImg, 100);
    if ($fileType == 'jpg') imagejpeg($imageInicial, $endImg, 100);
    if ($fileType == 'png') imagepng($imageInicial, $endImg, 9);
    if ($fileType == 'gif') imagegif($imageInicial, $endImg, 100);
}

// Function to assist the PNG images, sets the transparency in the image
private function setTransparency($new_image,$image_source){ 
    $transparencyIndex = imagecolortransparent($image_source); 
    $transparencyColor = array('red' => 255, 'green' => 255, 'blue' => 255);     
    if($transparencyIndex >= 0){
        $transparencyColor = imagecolorsforindex($image_source, $transparencyIndex);    
    }
    $transparencyIndex = imagecolorallocate($new_image, $transparencyColor['red'], $transparencyColor['green'], $transparencyColor['blue']); 
    imagefill($new_image, 0, 0, $transparencyIndex); 
    imagecolortransparent($new_image, $transparencyIndex);        
}

回答2:

public function redimesionImage($endThu,$newX,$newY,$endImg,$fileType){

    copy($endThu, $endImg);

    list($width, $height) = getimagesize($endImg);

    if($width >= $height) {

        $newXimage = $newX;

        $newYimage = ($height / $width) * $newXimage;

    } else {

        $newYimage = $newY;

        $newXimage = ($width / $height) * $newYimage;
    }

    $imageInicial = imagecreatetruecolor(ceil($newXimage), ceil($newYimage));

    if ($fileType == 'jpeg')   $endereco = imagecreatefromjpeg($endImg);
    if ($fileType == 'jpg')  $endereco = imagecreatefromjpeg($endImg);      
    if ($fileType == 'png')    {
        $endereco = imagecreatefrompng($endImg);
        imagealphablending($imageInicial, false);
        imagesavealpha($imageInicial,true);
        $transparent = imagecolorallocatealpha($imageInicial, 255, 255, 255, 127);
        imagefilledrectangle($endereco, 0, 0, $newXimage, $newYimage, $transparent);
    }
    if ($fileType == 'gif')  {
        $endereco = imagecreatefromgif($endImg);
        $this->setTransparency($imageInicial,$endereco);
    }

    imagecopyresampled($imageInicial, $endereco, 0, 0, 0, 0, ceil($newXimage), ceil($newYimage), ceil($width), ceil($height));

    if ($fileType == 'jpeg') imagejpeg($imageInicial, $endImg, 100);
    if ($fileType == 'jpg') imagejpeg($imageInicial, $endImg, 100);
    if ($fileType == 'png') imagepng($imageInicial, $endImg, 9);
    if ($fileType == 'gif') imagegif($imageInicial, $endImg, 100);
}
private function setTransparency($new_image,$image_source){ 
    $transparencyIndex = imagecolortransparent($image_source); 
    $transparencyColor = array('red' => 255, 'green' => 255, 'blue' => 255);     
    if($transparencyIndex >= 0){
        $transparencyColor = imagecolorsforindex($image_source, $transparencyIndex);    
    }
    $transparencyIndex = imagecolorallocate($new_image, $transparencyColor['red'], $transparencyColor['green'], $transparencyColor['blue']); 
    imagefill($new_image, 0, 0, $transparencyIndex); 
    imagecolortransparent($new_image, $transparencyIndex);        
}

回答3:

You use imagecreatefrompng() to load a picture, so you must make sure the picture format is png, not jpeg or other format. you can have a test use function imagecreatefromjpeg()

来源：https://stackoverflow.com/questions/24622948/creating-png-thumbnail-using-php