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Unit 11: Graphics

11.4.2 Changing the Output Format Notes
As you may have deduced, generating an image stream of a different type requires only two
changes to the script: send a different Content-Type and use a different image-generating
function. Example shows the JPEG version of the black square.
JPEG version of the black square.

<?php
$im = ImageCreate(200,200);
$white = ImageColorAllocate($im,0xFF,0xFF,0xFF);

$black = ImageColorAllocate($im,0x00,0x00,0x00);
ImageFilledRectangle($im,50,50,150,150,$black);
header(‘Content-Type: image/jpeg’);

ImageJPEG($im);
?>
11.4.3 Testing for Supported Image Formats

If you are writing code that must be portable across systems that may support different image
formats, use the ImageTypes( ) function to check which image types are supported. This
function returns a bitfield; you can use the bitwise AND operator (&) to check if a given bit
is set. The constants IMG_GIF, IMG_JPG, IMG_PNG, and IMG_WBMP correspond to the
bits for those image formats.

Example generates PNG files if PNG is supported, JPEG files if PNG is not supported, and GIF
files if neither PNG nor JPEG are supported.
Checking for image format support.

<?php

$im = ImageCreate(200,200);
$white = ImageColorAllocate($im,0xFF,0xFF,0xFF);
$black = ImageColorAllocate($im,0x00,0x00,0x00);
ImageFilledRectangle($im,50,50,150,150,$black);
if (ImageTypes( ) & IMG_PNG) {
header(“Content-Type: image/png”);
ImagePNG($im);
} elseif (ImageTypes( ) & IMG_JPG) {

header(“Content-Type: image/jpeg”);
ImageJPEG($im);
} elseif (ImageTypes( ) & IMG_GIF) {
header(“Content-Type: image/gif”);
ImageGIF($im);
}

?>

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