Pay attention to warning messages.

Set a region in which subsequent operations apply.

$cmd = "$input -region 140x120+50+20 -colorspace Gray"; 
exec("convert $cmd region_gray.jpg");

( Supported in ImageMagick 6 and 7.0.2-6 and above )

Reduce the number of colors in an image to the colors used by this image.

$cmd = "$input +dither ".
" -colors 24 -remap $input3";
exec("convert $cmd remap.jpg");
 

( Using the orange red gradiant to change the colours within the hibiscus photo )

Perform a remote operation.

Render vector operations.

Adjust the canvas and offset information of the image.

$cmd = "$input -crop 133x140+80+25 +repage"; 
exec("convert $cmd repage.jpg");

( Use +repage to completely remove/reset the virtual canvas meta-data from the images. )

Resample image to specified horizontal and vertical resolution.

$cmd = "$input -resample 30"; 
exec("convert $cmd resample.jpg");

Resize the image and leave EXIF data etc.

( Resize and thumbnail have the same effect but thumbnail strips the EXIF data etc. but leaves the colour profile on later versions. You can specify the filter to use - see filter. )

Settings remain in effect until parenthesis boundary.

Reverse the order of images in the current image list.

$cmd = "$input1 $input -reverse -gravity center". 
" -composite ";  
exec("convert $cmd reverse.jpg");

Rotate the image

$cmd = "$input -background transparent -rotate 30"; 
exec("convert $cmd rotate_30.png");

Scale image using pixel sampling.

$cmd = "$input -sample 100x100"; 
exec("convert $cmd sample.jpg");

Different type of resizing an image

$cmd = "$input -scale 133x100"; 
exec("convert $cmd scale.jpg");

( The -scale option uses a simpler, faster algorithm than -resize, and it ignores the -filter setting if one is present. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect. )