PHP image processing, php image processing

PHP provides some functions for editing and processing images. The most typical applications are random graphic verification codes, image watermarks and Generation of pie charts and bar charts in data statistics

Some graphics functions in PHP can be used directly, but most of them need to be installed after the GD2 function library is installed. Installing the GD2 library on the Windows platform is very simple, it is the php_gd2_dll file in the ext directory that comes with PHP5.

If not, it means that the GD2 library was not installed when installing PHP. Open the php.ini file and check the php.ini file (c:winsows) to see if there is a sentence ";extension = php_gd2.dll" (Paths and Directories) in the file. ), if there is, remove the ";" in it, and then set the value of the extension directory extension_dir in the file to the full path of PHP's ext directory, such as "extension_dir = E:php5ext", save and restart Apache

Drawing a graphic generally includes 4 steps: 1) Create a background, 2) Draw graphics or enter text in the background, 3) Output graphics, 4) Release all resources

Before this, please change the default output_buffering under Language Options in the php.ini file from off to on, and then restart Apache (Apache Restart), otherwise the following Warning will appear:

Cannot modify header information - headers already sent by.....

Example: Draw PNG graphics, such as drawing a straight line

<span>$image</span> = imagecreate(400,400);<span>//</span><span>創(chuàng)建一個圖像，兩個參數(shù)表示圖像的寬度和高度，單位為像素，并返回此圖像的數(shù)據(jù)流</span>
<span>$background_color</span> = imagecolorallocate(<span>$image</span>,255,255,255);<span>//</span><span>為圖像設(shè)置了白色的背景流,</span>
<span>$black</span> = imagecolorallocate(<span>$image</span>,0,0,0);<span>//</span><span>為圖像設(shè)置了黑色的背景流</span>
imageline(<span>$image</span>,0,0,100,100,<span>$black</span>);<span>//</span><span>繪制一條直線,并設(shè)置其顏色為黑色</span>
<span>ob_clean</span>();<span>//</span><span>清除輸出，否則圖像無法顯示</span>
<span>header</span>("Content-type:image/png");<span>//</span><span>向瀏覽器發(fā)送頭信息,輸出png圖片</span>
imagepng(<span>$image</span>);<span>//</span><span>輸出圖形</span>
imagedestroy(<span>$image</span>);<span>//</span><span>清除資源</span>

The image processing function can directly create an image stream to draw graphics, and can also read an existing image as an image stream, and then modify the image on a secondary basis, such as adding a watermark effect, etc. This function is often used to prevent pictures from being stolen

Example: Add a watermark URL to the original image (jpeg format)

    <span>ob_clean</span><span>();
    </span><span>header</span>("Content-type:image/jpeg"<span>);
    </span><span>$im</span> = imagecreatefromjpeg("dog.jpg"<span>);
    </span><span>$red</span> = imagecolorallocate(<span>$im</span>,255,0,0<span>);
    imagestring(</span><span>$im</span>,5,6,10,"http://www.cnblogs.com/520xiuge/",<span>$red</span><span>);
    imagejpeg(</span><span>$im</span><span>);
    imagedestroy(</span><span>$im</span>);