接着上一篇。GD库可以折腾很多用法出来，当然得跟画图相关，除了前面的验证码、水印外，还可以进行图片的缩放，裁剪、旋转等操作，这在很多应用中可以见到。
1. 加水印
前面已经知道，我们可以使用imagechar或者imagestring等将字符或字符串（甚至中文字符）绘制到图像上，以达到水印的目的，还有个更好的方式，不仅能加字符水印，还能加图片水印：imagecopy。
原型：bool imagecopy (resource $dst_im , resource $src_im , int $dst_x , int $dst_y , int $src_x , int $src_y , int $src_w , int $src_h)，看名字知道这是复制，第1、2个参数分别是目标图像句柄、源文件句柄，加水印时，如果水印图片是一张小图，加在一张大图上面，那么第一个参数就是大图句柄，第二个参数就是小图句柄。第3、4个参数是水印在目标图像上的x、y坐标值，第5、6个参数是水印图片上开始的x、y坐标值，第7、8个参数是水印图片即将要作为水印的宽和高，因此这个方法的意思就是，将水印图像src_im上左上角顶点坐标为（src_x, src_y）处，宽和高分别为src_w、src_h的部分复制到图像dst_im上，再将这个dst_im图像画到画布上保存或输出，即为加过水印后的图片了，代码：
<?<span>php
date_default_timezone_set(</span>'Asia/Shanghai'<span>);
</span><span>define</span>('DS',<span> DIRECTORY_SEPARATOR);
</span><span>//</span><span> 加水印，文字、图片水印，以图片为例</span>
<span>function</span> watermark(<span>$srcFile</span> = '', <span>$markFile</span> = '', <span>$dstFile</span> = ''<span>)
{
</span><span>if</span>(!<span>file_exists</span>(<span>$srcFile</span>) || !<span>file_exists</span>(<span>$markFile</span><span>))
{
</span><span>echo</span> 'file not exists!<br/>'<span>;
</span><span>return</span> <span>false</span><span>;
}
</span><span>//</span><span> 获取原始图片与水印图片的宽高</span>
<span>list</span>(<span>$srcWidth</span>, <span>$srcHeight</span>) = <span>getimagesize</span>(<span>$srcFile</span><span>);
</span><span>list</span>(<span>$markWidth</span>, <span>$markHeight</span>) = <span>getimagesize</span>(<span>$markFile</span><span>);
</span><span>//</span><span> 水印图片不能比原始图片像素还大</span>
<span>if</span>(<span>$markWidth</span> > <span>$srcWidth</span> || <span>$markHeight</span> > <span>$srcHeight</span><span>)
{
</span><span>return</span> <span>false</span><span>;
}
</span><span>//</span><span> 获取即将被加水印的原始图片句柄、水印图片句柄</span>
<span>$dstImg</span> = imagecreatefromjpeg(<span>$srcFile</span><span>);
</span><span>$markImg</span> = imagecreatefrompng(<span>$markFile</span><span>);
</span><span>//</span><span> 加水印的位置，简单放在右下角</span>
<span>$dst_x</span> = <span>$srcWidth</span> - <span>$markWidth</span><span>;
</span><span>$dst_y</span> = <span>$srcHeight</span> - <span>$markHeight</span><span>;
</span><span>//</span><span> 获取文件信息</span>
<span>$fileinfo</span> = <span>pathinfo</span>(<span>$srcFile</span><span>);
</span><span>if</span>(<span>empty</span>(<span>$dstFile</span><span>))
{
</span><span>$dstFile</span> = <span>rtrim</span>(<span>$fileinfo</span>['dirname'], DS).DS.'mark_'.<span>$fileinfo</span>['filename'].<span>date</span>('YmdHis').<span>mt_rand</span>(1, 1000).'.jpeg'<span>;
}
</span><span>//</span><span> 将水印图片复制到已有图片上</span>
imagecopy(<span>$dstImg</span>, <span>$markImg</span>, <span>$dst_x</span>, <span>$dst_y</span>, 0, 0, <span>$srcWidth</span>, <span>$srcHeight</span><span>);
</span><span>//</span><span> 将新加完水印的图片保存起来</span>
imagejpeg(<span>$dstImg</span>, <span>$dstFile</span><span>);
imagedestroy(</span><span>$dstImg</span><span>);
imagedestroy(</span><span>$markImg</span><span>);
</span><span>return</span> <span>true</span><span>;
}
</span><span>$srcFile</span> = 'G:\wamp\www\html\image\p125.jpg'; <span>//</span><span> 原图片</span>
<span>$markFile</span> = 'G:\wamp\www\html\image\ooopic_5.png'; <span>//</span><span> 水印图片</span>
watermark(<span>$srcFile</span>, <span>$markFile</span>); 效果： 
在这里，简单将水印图片放在图片右下角，所以放在图片的右下角要一个简单的计算，调用imagecopy时，从水印图片的左上角顶点（坐标0,0）开始全部（宽高传入水印图片宽高）复制到待加水印图片上，然后imagejpeg绘制图像并保存，注意类似imagejpeg（这里简单使用它）等绘图函数传入第二个参数时是保存图片为一个文件，而不是输出到浏览器，所以也不需调header函数发送头信息。
当然还要搞清楚哪是源文件（src），哪是目标文件（dst），把一张小图加水印到一张大图上时，源文件是小图水印，把它复制到大图上，大图就是目标。
能用图片作为水印，在于imagecopy的第二个参数是图像句柄，所以可以从现有图片来创建一个（如imagecreatefromjpeg），当然也能从现有的字符创建一个字符图像句柄变量---使用imagecreatefromstring方法，所以这个更通用。
2. 图片缩放
很多应用，图片列表是小图，当你点击某一个时，才会展现完整大图，这涉及到一个图片收缩的处理。有两个方法可供使用：imagecopyresized和imagecopyresampled，几乎一样，不同的是后者对图片进行重采样（貌似是我专业的词），所以成图质量更好（重采样的话也得看采取哪种方法，有的会变得更渣），挑一个说：
bool imagecopyresampled ( resource $dst_image , resource $src_image , int $dst_x , int $dst_y , int $src_x , int $src_y , int $dst_w , int $dst_h , int $src_w , int $src_h )
第一、二个参数与上面相似，如何做到缩放？比如这里，是将原图像上左上角顶点处，坐标为（src_x, src_y），宽高为src_w、src_h的部分图片，画到目标图像上坐标为（dst_x, dst_y），宽高为dst_w、dst_h的地方，所以如果目标图片上的宽高比原图上选取部分的宽高小的话，就成了缩小版了，当然还需要两个左上角顶点的坐标值相同，以jpg类型为例：
<?<span>php
date_default_timezone_set(</span>'Asia/Shanghai'<span>);
</span><span>define</span>('DS',<span> DIRECTORY_SEPARATOR);
</span><span>//</span><span> 缩小图片</span>
<span>/*</span><span>*
* @param src 原图像路径
* @param percent 缩小比例
* @param dstFile 保存图片的路径
</span><span>*/</span>
<span>function</span> zoomPic(<span>$srcFile</span> = '', <span>$percent</span> = 0.5, <span>$dstFile</span> = ''<span>)
{
</span><span>if</span>(!<span>file_exists</span>(<span>$srcFile</span><span>))
{
</span><span>return</span> <span>false</span><span>;
}
</span><span>list</span>(<span>$width</span>, <span>$height</span>) = <span>getimagesize</span>(<span>$srcFile</span>); <span>//</span><span> 获取宽高</span>
(<span>$percent</span> <= 0 || <span>$percent</span> > 1) && <span>$percent</span> = 0.5<span>;
</span><span>$newWidth</span> = <span>floor</span>(<span>$width</span> * <span>$percent</span>); <span>//</span><span> 缩小后的宽高</span>
<span>$newHeight</span> = <span>floor</span>(<span>$height</span> * <span>$percent</span><span>);
</span><span>$dstImg</span> = imagecreatetruecolor(<span>$newWidth</span>, <span>$newHeight</span>); <span>//</span><span> 创建新图像宽高的画布</span>
<span>$srcImg</span> = imagecreatefromjpeg(<span>$srcFile</span>); <span>//</span><span> 从原图像文件创建画布</span>
<span>$pathinfo</span> = <span>pathinfo</span>(<span>$srcFile</span><span>);
</span><span>if</span>(!<span>$dstFile</span>) <span>$dstFile</span> = <span>rtrim</span>(<span>$pathinfo</span>['dirname'], DS).DS.'zoom_'.<span>$pathinfo</span>['filename'].<span>date</span>('YmdHis').<span>mt_rand</span>(1, 1000).".jpeg"<span>;
</span><span>//</span><span> 从源文件左上角顶点开始进行缩小
//imagecopyresized($dstImg, $srcImg, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height); </span>
imagecopyresampled(<span>$dstImg</span>, <span>$srcImg</span>, 0, 0, 0, 0, <span>$newWidth</span>, <span>$newHeight</span>, <span>$width</span>, <span>$height</span><span>);
</span><span>//</span><span> 绘制且保存图像</span>
imagejpeg(<span>$dstImg</span>, <span>$dstFile</span><span>);
</span><span>//</span><span> 销毁资源</span>
imagedestroy(<span>$dstImg</span><span>);
imagedestroy(</span><span>$srcImg</span><span>);
</span><span>return</span> <span>true</span><span>;
}
</span><span>//</span><span> 测试</span>
<span>$srcFile</span> = 'G:\wamp\www\html\image\p179.jpg'<span>;
zoomPic(</span><span>$srcFile</span>); 效果：
在这里，我们可以将原图与小图分两套存放，列表展示小图，低级查就展示原图。
3. 图片裁剪
考虑上面的imagecopyresampled方法，如果不从原图像的左上角开始，而是左上角偏右下某一点开始，切图的宽高也再等于源文件完整的宽高，而是部分宽高，那么新的重采样的图片，就是源图片的一部分，就达到了裁剪的效果，所以裁剪与缩放使用的方法一样
<?<span>php
date_default_timezone_set(</span>'Asia/Shanghai'<span>);
</span><span>define</span>('DS',<span> DIRECTORY_SEPARATOR);
</span><span>//</span><span> cut a picture</span>
<span>function</span> cutPic(<span>$srcFile</span> = '', <span>$x</span> = 0, <span>$y</span> = 0, <span>$width</span> = 16, <span>$height</span> = 16, <span>$dstFile</span> = ''<span>)
{
</span><span>if</span>(!<span>file_exists</span>(<span>$srcFile</span><span>))
{
</span><span>return</span> <span>false</span><span>;
}
</span><span>list</span>(<span>$srcWidth</span>, <span>$srcHeight</span>, <span>$type</span>) = <span>getimagesize</span>(<span>$srcFile</span><span>);
</span><span>$x</span> < 0 && <span>$x</span> = 0<span>;
</span><span>$y</span> < 0 && <span>$y</span> = 0<span>;
</span><span>//</span><span> 宽高设置</span>
((<span>$width</span> + <span>$x</span>) > <span>$srcWidth</span>) && <span>$width</span> = <span>$srcWidth</span><span>;
((</span><span>$height</span> + <span>$y</span>) > <span>$srcHeight</span>) && <span>$height</span> = <span>$srcHeight</span><span>;
(</span><span>$width</span> <= 0) && <span>$width</span> = <span>$srcWidth</span><span>;
(</span><span>$height</span> <= 0) && <span>$height</span> = <span>$srcHeight</span><span>;
</span><span>$dstImg</span> = imagecreatetruecolor(<span>$width</span>, <span>$height</span>); <span>//</span><span> 目标文件资源 </span>
<span>switch</span>(<span>$type</span><span>)
{
</span><span>case</span> IMG_GIF:
<span>$srcImg</span> = imagecreatefromgif(<span>$srcFile</span>); <span>//</span><span> 获取源文件资源句柄及扩展名处理，以使用合适的函数和扩展</span>
<span>$ext</span> = 'gif'<span>;
</span><span>$imagefun</span> = 'imagegif'<span>;
</span><span>break</span><span>;
</span><span>case</span> IMG_JPG:
<span>$srcImg</span> = imagecreatefromjpeg(<span>$srcFile</span><span>);
</span><span>$ext</span> = 'jpeg'<span>;
</span><span>$imagefun</span> = 'imagejpeg'<span>;
</span><span>break</span><span>;
</span><span>default</span>:
<span>$srcImg</span> = imagecreatefrompng(<span>$srcFile</span><span>);
</span><span>$ext</span> = 'png'<span>;
</span><span>$imagefun</span> = 'imagepng'<span>;
</span><span>break</span><span>;
}
</span><span>//</span><span> 设置保存剪切后的文件路径</span>
<span>$fileinfo</span> = <span>pathinfo</span>(<span>$srcFile</span><span>);
</span><span>if</span>(<span>empty</span>(<span>$dstFile</span><span>))
{
</span><span>$dstFile</span> = <span>rtrim</span>(<span>$fileinfo</span>['dirname'], DS).DS.'cut_'.<span>$fileinfo</span>['filename'].<span>date</span>('YmdHis').<span>mt_rand</span>(1, 1000).".{<span>$ext</span>}"<span>;
}
</span><span>//</span><span> 执行剪切操作</span>
imagecopyresampled(<span>$dstImg</span>, <span>$srcImg</span>, 0, 0, <span>$x</span>, <span>$y</span>, <span>$width</span>, <span>$height</span>, <span>$width</span>, <span>$height</span><span>);
</span><span>//</span><span> 画于画布并保存文件</span>
<span>$imagefun</span>(<span>$dstImg</span>, <span>$dstFile</span><span>);
imagedestroy(</span><span>$dstImg</span><span>);
imagedestroy(</span><span>$srcImg</span><span>);
</span><span>return</span> <span>true</span><span>;
}
</span><span>//</span><span> 测试</span>
<span>$srcFile</span> = 'G:\wamp\www\html\image\p221.jpg'<span>;
cutPic(</span><span>$srcFile</span>, 50, 50, 50, 50); 效果：
常见的应用是，我们在给自己的某个应用换头像时，头像太大，就会用到裁剪，用这就可以做一个模拟实现。
4. 图片旋转
图片旋转也十分常见，主要用到函数imagerotate，原型:resource imagerotate ( resource $image , float $angle , int $bgd_color [, int $ignore_transparent = 0 ] )，第一个参数是待旋转图像句柄，第二个参数angle 是旋转的角度数值，第三个参数指定一个颜色，即当旋转后出现空的地方是使用哪种颜色填充，第四个参数是指定一个透明色，默认0表示保留透明色。该方法返回一个新的图像句柄，就是经过旋转后的图像资源变量，将它绘制保存即可。还要注意的是，旋转的角度可以指定0到360之间，为逆时针旋转，以jpg为例：
<?<span>php
date_default_timezone_set(</span>'Asia/Shanghai'<span>);
</span><span>define</span>('DS',<span> DIRECTORY_SEPARATOR);
</span><span>/*</span><span>*
* 图片旋转
* @param angular 旋转角度值 0-360
</span><span>*/</span>
<span>function</span> rotatePic(<span>$srcFile</span> = '', <span>$angular</span> = 0, <span>$dstFile</span> = ''<span>)
{
</span><span>if</span>(!<span>file_exists</span>(<span>$srcFile</span><span>))
{
</span><span>echo</span> 'file not exists<br/>'<span>;
</span><span>return</span> <span>false</span><span>;
}
</span><span>$srcImg</span> = imagecreatefromjpeg(<span>$srcFile</span><span>);
</span><span>//</span><span> 处理保存文件地址</span>
<span>$fileinfo</span> = <span>pathinfo</span>(<span>$srcFile</span><span>);
</span><span>if</span>(<span>empty</span>(<span>$dstFile</span><span>))
{
</span><span>$dstFile</span> = <span>rtrim</span>(<span>$fileinfo</span>['dirname'], DS).DS.'rotate_'.<span>$fileinfo</span>['filename'].<span>date</span>('YmdHis').<span>mt_rand</span>(1, 1000).'.jpeg'<span>;
}
</span><span>$white</span> = imagecolorallocate(<span>$srcImg</span>, 0xff, 0xff, 0xf1<span>);
</span><span>//</span><span> 执行旋转，注意是逆时针方向</span>
<span>$dstImg</span> = imagerotate(<span>$srcImg</span>, <span>$angular</span>, <span>$white</span><span>);
</span><span>//</span><span> 画到画布，保存文件</span>
imagejpeg(<span>$dstImg</span>, <span>$dstFile</span><span>);
imagedestroy(</span><span>$dstImg</span><span>);
imagedestroy(</span><span>$srcImg</span><span>);
</span><span>return</span> <span>true</span><span>;
}
</span><span>//</span><span> 测试</span>
<span>$srcFile</span> = 'G:\wamp\www\html\image\p219.jpg'<span>;
rotatePic(</span><span>$srcFile</span>, 220); 效果：原图
旋转后
5. 图片翻转
这个在应用中不那么常见。所谓翻转，就是对图像进行镜面翻转，比如以图片中间竖直线为轴线，左边换到右边，右边换到左边，对调一下位置，就是左右翻转。想象一下，以中间竖直线为对称轴的情况，Y轴像素点不变，X轴上的像素点左右对调，仍可以使用imagecopy方法，对于源文件，在复制到目标图像时，进行这个操作，以绕Y轴旋转，jpg类型图片为例
<?<span>php
</span><span>//</span><span> 图片翻转</span>
date_default_timezone_set('Asia/Shanghai'<span>);
</span><span>define</span>('DS',<span> DIRECTORY_SEPARATOR);
</span><span>//</span><span> 沿Y轴翻转，x坐标值对调</span>
<span>function</span> turnY(<span>$srcFile</span> = '', <span>$dstFile</span> = ''<span>)
{
</span><span>if</span>(!<span>file_exists</span>(<span>$srcFile</span><span>))
{
</span><span>return</span> <span>false</span><span>;
}
</span><span>//</span><span> 原图像句柄和宽高获取</span>
<span>$srcImg</span> = imagecreatefromjpeg(<span>$srcFile</span><span>);
</span><span>$srcWidth</span> = imagesx(<span>$srcImg</span><span>);
</span><span>$srcHeight</span> = imagesy(<span>$srcImg</span><span>);
</span><span>$dstImg</span> = imagecreatetruecolor(<span>$srcWidth</span>, <span>$srcHeight</span><span>);
</span><span>//</span><span> 沿Y轴翻转，x轴上的像素点左右对调</span>
<span>for</span>(<span>$i</span> = 0; <span>$i</span> < <span>$srcWidth</span>; <span>$i</span>++<span>)
{
imagecopy(</span><span>$dstImg</span>, <span>$srcImg</span>, <span>$srcWidth</span>-<span>$i</span>-1, 0, <span>$i</span>, 0, 1, <span>$srcHeight</span><span>);
}
</span><span>//</span><span> 画像保存路径处理</span>
<span>$fileinfo</span> = <span>pathinfo</span>(<span>$srcFile</span><span>);
</span><span>if</span>(<span>empty</span>(<span>$dstFile</span><span>))
{
</span><span>$dstFile</span> = <span>rtrim</span>(<span>$fileinfo</span>['dirname'], DS).DS.'turnx_'.<span>$fileinfo</span>['filename'].<span>date</span>('YmdHis').<span>mt_rand</span>(1, 1000).'.jpeg'<span>;
}
</span><span>//</span><span> 绘制图像，保存文件</span>
imagejpeg(<span>$dstImg</span>, <span>$dstFile</span><span>);
imagedestroy(</span><span>$dstImg</span><span>);
imagedestroy(</span><span>$srcImg</span><span>);
</span><span>return</span> <span>false</span><span>;
}
</span><span>//</span><span> 测试</span>
<span>$srcFile</span> = 'G:\wamp\www\html\image\p311.jpg'<span>;
turnY(</span><span>$srcFile</span>); 效果： 翻转前
翻转后 
主要就是for循环那儿，得到源文件的宽度$srcWidth后，如果源文件上坐标是（$i, 0）则对应目标图像上坐标（$srcWidth-$i-1, 0），然后将宽度为1个像素，高为源文件整个高度$srcHeight的资源复制过去，循环完成后就全部复制到一个图片上了，相当于是一条一条线的画过去的。
无意浏览手册感觉被坑，看到imageflip函数猜到是这个功能，一看果然是的，可是看的书已经落后几年了，原型：bool imageflip ( resource $image , int $mode )，第一个参数是目标图像资源，第二个参数是翻转的方式，使用php自带的枚举变量即可，有IMG_FLIP_HORIZONTAL（水平）、IMG_FLIP_HORIZONTAL（竖直）、IMG_FLIP_BOTH（水平竖直）三种方式，一个函数即可实现。
反正都挺简单，不如练练手玩玩 :-D
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