Summary of several functions of PHP GD library to generate images, phpgd_PHP tutorial

A summary of several functions of PHP GD library to generate images, phpgd

After dynamically drawing the image using the functions provided in the GD library, you need to output it to the browser or save the image. In PHP, the dynamically drawn canvas can be directly generated into four image formats: GIF, JPEG, PNG and WBMP. Images in these formats can be generated by calling the following four functions:

Copy code The code is as follows:

bool imagegif(resource $image[,string $filename]) //Output the image in GIF format
bool imagejpeg(resource $image[,string $filename[,int $quality]]) //Output the image in JPEG format
bool imagepng(resource $image[,string $filename]) //Output the image in PNG format
bool imagewbmp(resource $image[,string $filename[,int $foreground]]) //Output the image in WBMP format

The use of the above four functions is similar, and the use of the first two parameters is the same. The first parameter $image is required and is the image reference handle introduced earlier. If these functions provide other parameters, the original image will be streamed directly when accessed, and the dynamically output image will be displayed in the browser. But you must use the header() function to send header information before output, which is used to notify the browser to use the correct MIME type to parse the received content, so that it knows that we are sending images instead of text-like HTML. The following code snippet automatically detects the image types supported by the GD library to write a more portable PHP program. As shown below:

Copy code The code is as follows:

If(function_exists("imagegif")){ //Determine whether the function that generates GIF format images exists
header("Content-type:image/gif"); //Send header information and set the MIME type to image/gif
imagegif($im); //Output the image to the browser in GIF format
}elseif(function_exists("imageipeg")){
         header("Content-type:image/jpeg");
Imagejpeg($im,"",0.5);
}elseif(function_exists("imagepng")){
header("Content-type:image/png");
Imagepng($im);
}elseif(function_exists("imagewbmp")){
         header("Content-type:image/wbmp");
Imagewbmp($im);
}else{
​​​​​die("In PHP server, images are not supported");
}
?>

If you wish to save PHP dynamically drawn images on your local server, you must specify a filename string in the second optional parameter. Not only does this not output the image directly to the browser, it also eliminates the need to use the header() function to send header information. If you use the imageJPEG() function to generate an image in JPEG format, you can also specify the quality of the JPEG format image through the third optional parameter $quality. The value that this parameter can provide is from 0 (worst quality, but smallest file) to 100 (Highest quality, largest file) integer, the default value is 75. You can also provide the third optional parameter $forground to the function imageWBMP() to specify the foreground color of the image. The default color value is black.

http://www.bkjia.com/PHPjc/914045.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/914045.htmlTechArticleA summary of several functions for generating images in the PHP GD library. After phpgd uses the functions provided in the GD library to dynamically draw the image. , you need to output to the browser or save the image. In PHP,...