Generating Pure Image Background

convert -size 1366x768 canvas:yellow  yello_bg.gif

Changing image background

# `-flatten` must be specified
convert in.png -background white -flatten out.png
#or use
convert in.png -fill '#CCCCCC00' -opaque none out.png

Resizing Image

# ImageMagick will try to preserve the aspect ratio
convert -resize 128x128 icon.png icon-128.png
convert -adaptive-resize 128x128 icon.png icon-128.png

# Force the image to become a specific size – even if it messes up the aspect ratio, you can add an exclamation point to the dimensions
convert -resize 128x128! icon.png icon-128.png

Compressing Image

convert -strip -interlace Plane -gaussian-blur 0.05 -quality 85% source.jpg result.jpg

Open Source Image Resource on the Internet

• Creative Commons Search
• PhotoPin
• Search Flickr with Creative Commons License
• For more, visit here

Reference

• imagemagick usage guide
• compressing image by stackoverflow
• resize imgae by howtogeek