Home Backend Development PHP Tutorial 使用PHP缩略图跟剪切图

使用PHP缩略图跟剪切图

Jun 13, 2016 pm 12:32 PM
int resource src

使用PHP缩略图和剪切图
API:
resource imagecreatetruecolor ( int $width , int $height )
magecreatetruecolor() 返回一个图像标识符,代表了一幅大小为 x_size 和 y_size 的黑色图像。

是否定义了本函数取决于 PHP 和 GD 的版本。从 PHP 4.0.6 到 4.1.x 只要加载了 GD 模块本函数一直存在,但是在没有安装 GD2 的时候调用,PHP 将发出致命错误并退出。在 PHP 4.2.x 中此行为改为发出警告而不是错误。其它版本只在安装了正确的 GD 版本时定义了本函数。

bool imagecopy ( resource $dst_im , resource $src_im , int $dst_x , int $dst_y , int $src_x , int $src_y , int $src_w , int $src_h )
将 src_im 图像中坐标从 src_x,src_y 开始,宽度为 src_w,高度为 src_h 的一部分拷贝到 dst_im 图像中坐标为 dst_x 和 dst_y 的位置上。

bool imagejpeg ( resource $image [, string $filename [, int $quality ]] )
imagejpeg() 从 image 图像以 filename 为文件名创建一个 JPEG 图像。

ool imagedestroy ( resource $image )
imagedestroy() 释放与 image 关联的内存。image 是由图像创建函数返回的图像标识符,例如 imagecreatetruecolor()。



http://www.cnblogs.com/xiaomia/archive/2010/11/13/1876191.html
一开始采用了 imagecopyresized 方法进行图像等比缩小,实际操作后发现,图像缩小后燥点非常严重。后再换用 imagecopysampled 方法,该方法会对图像进行重新采样,对缩小的图像进行平滑处理,使清晰度得到很大提高

list($src_w,$src_h)=getimagesize($src_img);  // 获取原图尺寸

$dst_scale = $dst_h/$dst_w; //目标图像长宽比
$src_scale = $src_h/$src_w; // 原图长宽比

if($src_scale>=$dst_scale){  // 过高
$w = intval($src_w);
$h = intval($dst_scale*$w);

$x = 0;
$y = ($src_h - $h)/3;
}
else{ // 过宽
$h = intval($src_h);
$w = intval($h/$dst_scale);

$x = ($src_w - $w)/2;
$y = 0;
}

// 剪裁
$source=imagecreatefromjpeg($src_img);
$croped=imagecreatetruecolor($w, $h);
imagecopy($croped,$source,0,0,$x,$y,$src_w,$src_h);

// 缩放
$scale = $dst_w/$w;
$target = imagecreatetruecolor($dst_w, $dst_h);
$final_w = intval($w*$scale);
$final_h = intval($h*$scale);
imagecopyresampled($target,$croped,0,0,0,0,$final_w,$final_h,$w,$h);

// 保存
$timestamp = time();
imagejpeg($target, "$timestamp.jpg");
imagedestroy($target);
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http://www.cnblogs.com/analyzer/articles/1267017.html
先说说缩略图,它用得比较多,代码如下:
<?php    
 header("Content-type: image/png");    
 //原图    
 $filename='source.jpg';    
 //缩放比例 新图/原图    
 $percent = '0.5';    
 list($width,$height) = getimagesize($filename);    
 $newwidth = $width * $percent;    
 $newheight = $height * $percent;    
// Load    
$thumb = imagecreatetruecolor($newwidth, $newheight);    
$source = imagecreatefromjpeg($filename);    
// Resize    
imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);    
// Output    
imagepng($thumb);    
?> 
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再说说剪切图,就是不缩放,而是从原图中剪切出一块小图,比较个性。代码如下:
<?php    
 $maxW=300;    
 $maxH=300;    
 //图片路径    
 $link= "big.jpg";    
 $img = imagecreatefromjpeg($link);    
 list($width, $height, $type, $attr) = getimagesize($link);    
 $widthnum=ceil($width/$maxW);    
 $heightnum=ceil($height/$maxH);    
$iOut = imagecreatetruecolor ($maxW,$maxH);    
//bool imagecopy ( resource dst_im, resource src_im, int dst_x, int dst_y, int src_x, int src_y, int src_w, int src_h )    
//将 src_im 图像中坐标从 src_x,src_y 开始,宽度为 src_w,高度为 src_h 的一部分拷贝到 dst_im 图像中坐标为 dst_x 和 dst_y 的位置上。    
   
//整图循环切割    
for ($i=0;$i < $heightnum;$i++) {    
 for ($j=0;$j < $widthnum;$j++) {    
 imagecopy($iOut,$img,0,0,($j*$maxW),($i*$maxH),$maxW,$maxH);//复制图片的一部分    
 imagejpeg($iOut,"images/".$i."_".$j.".jpg"); //输出成0_0.jpg,0_1.jpg这样的格式    
 }    
}    
   
//只剪切一个开始部位的小图.复制图片的一部分    
 imagecopy($iOut,$img,0,0,0,0,$maxW,$maxH);    
 imagejpeg($iOut,"images/sm.jpg");    
?>
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