Programming PHP

You can also take this a step further and get your button.php script to support multiple
image types. Simply check $ext and call the appropriate ImagePNG( ), ImageJPEG( ),
or ImageGIF( ) function at the end of the script. You can also parse the filename and
add modifiers such as color, size, and font, or pass them right in the URL. Because of
the parse_str( ) call in the example, a URL such as http://your.site/buttons/php.
png?size=16 displays “php” in a font size of 16.
Scaling Images
There are two ways to change the size of an image. The ImageCopyResized( ) function
is available in all versions of GD, but its resizing algorithm is crude and may lead
to jagged edges in your newimages. The ImageCopyResampled( ) function is newin
GD 2.x and features pixel interpolation to give smooth edges and clarity to resized
images (it is, however, slower than ImageCopyResized( )). Both functions take the
same arguments:
ImageCopyResized(dest, src, dx, dy, sx, sy, dw, dh, sw, sh);
ImageCopyResampled(dest, src, dx, dy, sx, sy, dw, dh, sw, sh);
The dest and src parameters are image handles. The point (dx,dy) is the point in the
destination image where the region will be copied. The point (sx,sy) is the upperleft
corner of the source image. The sw, sh, dw, and dh parameters give the width and
height of the copy regions in the source and destination.
Example 9-10 takes the php.jpg image shown in Figure 9-8 and smoothly scales it
down to one-quarter of its size, yielding the image in Figure 9-9.
Figure 9-8. Original php.jpg image
Example 9-10. Resizing with ImageCopyResampled( )