我想在PHP中裁剪一张图片并保存文件。我知道应该使用GD库,但不确定如何操作。有什么建议吗?
谢谢
你可以使用 imagecopy
来裁剪图片的特定部分。命令如下:
imagecopy (
resource $dst_im - the image object ,
resource $src_im - destination image ,
int $dst_x - x coordinate in the destination image (use 0) ,
int $dst_y - y coordinate in the destination image (use 0) ,
int $src_x - x coordinate in the source image you want to crop ,
int $src_y - y coordinate in the source image you want to crop ,
int $src_w - crop width ,
int $src_h - crop height
)
来自PHP.net的代码-从源图像中裁剪出一个80x40像素的图像。
<?php
// Create image instances
$src = imagecreatefromgif('php.gif');
$dest = imagecreatetruecolor(80, 40);
// Copy
imagecopy($dest, $src, 0, 0, 20, 13, 80, 40);
// Output and free from memory
header('Content-Type: image/gif');
imagegif($dest);
imagedestroy($dest);
imagedestroy($src);
?>
这个函数将裁剪图像并保持图像纵横比 :)
function resize_image_crop($image, $width, $height)
{
$w = @imagesx($image); //current width
$h = @imagesy($image); //current height
if ((!$w) || (!$h)) { $GLOBALS['errors'][] = 'Image couldn\'t be resized because it wasn\'t a valid image.'; return false; }
if (($w == $width) && ($h == $height)) { return $image; } //no resizing needed
$ratio = $width / $w; //try max width first...
$new_w = $width;
$new_h = $h * $ratio;
if ($new_h < $height) { //if that created an image smaller than what we wanted, try the other way
$ratio = $height / $h;
$new_h = $height;
$new_w = $w * $ratio;
}
$image2 = imagecreatetruecolor ($new_w, $new_h);
imagecopyresampled($image2,$image, 0, 0, 0, 0, $new_w, $new_h, $w, $h);
if (($new_h != $height) || ($new_w != $width)) { //check to see if cropping needs to happen
$image3 = imagecreatetruecolor ($width, $height);
if ($new_h > $height) { //crop vertically
$extra = $new_h - $height;
$x = 0; //source x
$y = round($extra / 2); //source y
imagecopyresampled($image3,$image2, 0, 0, $x, $y, $width, $height, $width, $height);
} else {
$extra = $new_w - $width;
$x = round($extra / 2); //source x
$y = 0; //source y
imagecopyresampled($image3,$image2, 0, 0, $x, $y, $width, $height, $width, $height);
}
imagedestroy($image2);
return $image3;
} else {
return $image2;
}
}
imagecopyresampled
方法的“示例1”,它会向您展示如何裁剪和输出图像,您只需要添加一些代码来捕获并将输出写入文件即可...
http://us2.php.net/manual/en/function.imagecopyresampled.php
还有其他选项,包括 Image Magick,如果在您的服务器上安装了它,可以直接使用 PHP 的 exec
方法(或类似方法)访问,或者您可以安装 PHP Imagick 扩展,这将产生更高质量的图像,并且在我看来,更加直观和灵活。
最后,我使用了开源的 PHPThumb 类库,它具有相当简单的界面,并且可以根据服务器上的情况使用多个选项,包括 ImageMagick 和 GD。
我在一些项目中使用这个脚本,它非常容易使用: http://shiftingpixel.com/2008/03/03/smart-image-resizer/
该脚本需要 PHP 5.1.0(自2005-11-24发布以来已经过时 - 如果还没有升级到此版本,现在是时候升级了)和 GD(良好的 Web 主机很少缺少)。
以下是在 HTML 中使用它的示例:
<img src="/image.php/coffee-bean.jpg?width=200&height=200&image=/wp-content/uploads/2008/03/coffee-bean.jpg" alt="Coffee Bean" />
我刚刚创建了这个函数,它可以满足我的需求,创建一个居中且裁剪的缩略图。它非常简洁,不需要像webGautam的答案中那样多次调用imagecopy。
提供图片路径、最终宽度和高度,以及可选的图片质量。我为创建缩略图而制作了这个函数,因此所有图片都保存为JPG格式,如果您需要其他图片类型,可以编辑它来适应。这里的重点是使用imagecopyresampled方法进行数学计算和生成缩略图的方法。图像使用相同的名称保存,加上图像大小。
function resize_crop_image($image_path, $end_width, $end_height, $quality = '') {
if ($end_width < 1) $end_width = 100;
if ($end_height < 1) $end_height = 100;
if ($quality < 1 || $quality > 100) $quality = 60;
$image = false;
$dot = strrpos($image_path,'.');
$file = substr($image_path,0,$dot).'-'.$end_width.'x'.$end_height.'.jpg';
$ext = substr($image_path,$dot+1);
if ($ext == 'jpg' || $ext == 'jpeg') $image = @imagecreatefromjpeg($image_path);
elseif($ext == 'gif') $image = @imagecreatefromgif($image_path);
elseif($ext == 'png') $image = @imagecreatefrompng($image_path);
if ($image) {
$width = imagesx($image);
$height = imagesy($image);
$scale = max($end_width/$width, $end_height/$height);
$new_width = floor($scale*$width);
$new_height = floor($scale*$height);
$x = ($new_width != $end_width ? ($width - $end_width) / 2 : 0);
$y = ($new_height != $end_height ? ($height - $end_height) / 2 : 0);
$new_image = @imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($new_image,$image,0,0,$x,$y,$new_width,$new_height,$width - $x,$height - $y);
imagedestroy($image);
imagejpeg($new_image,$file,$quality);
imagedestroy($new_image);
return $file;
}
return false;
}
/*parameters are
$image =source image name
$width = target width
$height = height of image
$scale = scale of image*/
function resizeImage($image,$width,$height,$scale) {
//generate new image height and width of source image
$newImageWidth = ceil($width * $scale);
$newImageHeight = ceil($height * $scale);
//Create a new true color image
$newImage = imagecreatetruecolor($newImageWidth,$newImageHeight);
//Create a new image from file
$source = imagecreatefromjpeg($image);
//Copy and resize part of an image with resampling
imagecopyresampled($newImage,$source,0,0,0,0,$newImageWidth,$newImageHeight,$width,$height);
//Output image to file
imagejpeg($newImage,$image,90);
//set rights on image file
chmod($image, 0777);
//return crop image
return $image;
}