Hello there friends! I hope you all are enjoying a beautiful day…creating awesome designs!
I have a question. Let’s say I design a wallpaper for 1920×1080 px and now I want to resize the same wallpaper to fit the iphone, ipad, different resolutions, other phones displays.
Is there any easy / fast way to do this? Or do you have to create / resize the canvas in photoshop/illustrator?
Reading other designer ideas will get me some insight. Thank you so much!
Open PS >Open file > Click Image > Image Size. 
You can’t do it with Image Size, because you need different proportions and you might loose quality. I usually resize the canvas or make new canvases first in needed sizes and then duplicate the graphic from the original (Layers panel > Duplicate Layers). Crop Tool might work as well. It really depends on what kind of graphic you have.
thanks everybody!
