PHP: Resize image - preserve ratio of width and height

resize_image.php

/**
 * Resize image - preserve ratio of width and height.
 * @param string $sourceImage path to source JPEG image
 * @param string $targetImage path to final JPEG image file
 * @param int $maxWidth maximum width of final image (value 0 - width is optional)
 * @param int $maxHeight maximum height of final image (value 0 - height is optional)
 * @param int $quality quality of final image (0-100)
 * @return bool
 */
function resizeImage($sourceImage, $targetImage, $maxWidth, $maxHeight, $quality = 80)
{
    // Obtain image from given source file.
    if (!$image = @imagecreatefromjpeg($sourceImage))
    {
        return false;
    }

    // Get dimensions of source image.
    list($origWidth, $origHeight) = getimagesize($sourceImage);

    if ($maxWidth == 0)
    {
        $maxWidth  = $origWidth;
    }

    if ($maxHeight == 0)
    {
        $maxHeight = $origHeight;
    }

    // Calculate ratio of desired maximum sizes and original sizes.
    $widthRatio = $maxWidth / $origWidth;
    $heightRatio = $maxHeight / $origHeight;

    // Ratio used for calculating new image dimensions.
    $ratio = min($widthRatio, $heightRatio);

    // Calculate new image dimensions.
    $newWidth  = (int)$origWidth  * $ratio;
    $newHeight = (int)$origHeight * $ratio;

    // Create final image with new dimensions.
    $newImage = imagecreatetruecolor($newWidth, $newHeight);
    imagecopyresampled($newImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $origWidth, $origHeight);
    imagejpeg($newImage, $targetImage, $quality);

    // Free up the memory.
    imagedestroy($image);
    imagedestroy($newImage);

    return true;
}

/**
 * Example
 * resizeImage('image.jpg', 'resized.jpg', 200, 200);
 */
 

not working

if original is w: 2448, h: 3264
and desired is w: 1500, h: 500

@kriit24

the code is clear, preserving the ratio is a primary goal, because it uses the lowest scaling ratio either width or height
$ratio = min($widthRatio, $heightRatio);

Also your example is about distortion, not preserved scale:
w: 2448, h: 3264 - portrait orientation , aspect ratio 3:4
w: 1500, h: 500 - landscape orientation, aspect ratio 3:1

Elegant, easy, nice ! thanks

png is not working.

@narenthiran The resizeImage function only works with JPEG images.

Okay i found another solution. Thanks.

Added PNG support in fork.

thanks

Giải quyết tất cả vấn đề với mọi loại hình ảnh (Solve all problems with all types of images)

function resizeImage($sourceImage, $targetImage, $maxWidth, $maxHeight, $quality = 80)
{
list($origWidth, $origHeight, $type) = getimagesize($sourceImage);

if ($type == 1)
{
    header ('Content-Type: image/gif');
    $image = imagecreatefromgif($sourceImage);
}
elseif ($type == 2)
{
    header ('Content-Type: image/jpeg');
    $image = imagecreatefromjpeg($sourceImage);
}
elseif ($type == 3)
{
    header ('Content-Type: image/png');
    $image = imagecreatefrompng($sourceImage);
}
else
{
    header ('Content-Type: image/x-ms-bmp');
    $image = imagecreatefromwbmp($sourceImage);
}

if ($maxWidth == 0)
{
    $maxWidth  = $origWidth;
}

if ($maxHeight == 0)
{
    $maxHeight = $origHeight;
}

// Calculate ratio of desired maximum sizes and original sizes.
$widthRatio = $maxWidth / $origWidth;
$heightRatio = $maxHeight / $origHeight;

// Ratio used for calculating new image dimensions.
$ratio = min($widthRatio, $heightRatio);

// Calculate new image dimensions.
$newWidth  = (int)$origWidth  * $ratio;
$newHeight = (int)$origHeight * $ratio;

// Create final image with new dimensions.

// if($type==1 or $type==3)
// {
//    $newImage = imagefill($newImage,0,0,0x7fff0000);
// }

$newImage = imagecreatetruecolor($newWidth, $newHeight);

$transparent = imagecolorallocatealpha($newImage, 0, 0, 0, 127);
imagefill($newImage, 0, 0, $transparent);
imagesavealpha($newImage, true);


imagecopyresampled($newImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $origWidth, $origHeight);
imagepng($newImage, $targetImage);

// Free up the memory.
imagedestroy($image);
imagedestroy($newImage);

return true;

}

Everything works fine except PNG transparency. I am getting a black background on all PNGs.

work awesome!