RE: [PHP] Advanced maths help (for GD image functionality)

Algebra! I aced that in 7th grade! (don't ask me about all the other years of math. Haha.. I think I just got bored and slept a lot or something) -TG > -----Original Message----- > From: Jonel Rienton [mailto:jonel@road14.com] > Sent: Friday, October 15, 2004 11:02 AM > To: Gryffyn, Trevor > Cc: php php; Mag > Subject: Re: [PHP] Advanced maths help (for GD image functionality) > > > it's algebra at work :) > > nicely done. > > > On Oct 15, 2004, at 8:57 AM, Gryffyn, Trevor wrote: > > > Good questions.. Here's some stuff to play with: > > > >> Heres my maths problems in 2 parts: > >> > >> Problem 1) > >> I need to scale down an image (eg: example.jpg) to > >> height of 120 pixels while maintaining the images > >> proportions. > >> > >> eg: > >> if i have an image of (height and width) 800x600 what > >> would the dimensions be if the height was 120? > > > > Proportions can be figured out by doing cross multiplication. Say > > you're trying to figure out percentages, do something like this: > > > > x 75 > > ----- x ------- > > 100 185 > > > > > > Multiple cross ways and you get: > > > > 185x = 7500 > > > > Divide both sides by 185 to get just an "x = " and you get > 40.54. 75 > > is 40.54% of 185. > > > > > > You can use this to get your proportions for images too. It doesn't > > have to be 100 at the bottom of that one side. Say you > have an image > > that's 1275 x 852 and you want to create a 120 x ???? Thumbnail. > > > > > > 1275 w 120 w > > ------ x ------- > > 852 h x h > > > > > > > > 1275x = 102240 (1275 times x = 120 times 852) > > > > Divide both sides by 1275 and you get: > > > > X = 80.19.... Which you might round to 80. > > > > > > So a 1275 x 852 image scale down to 120 x 80. > > > > Easy, right? :) > > > > > >> Problem 2) > >> After getting the above image now I need the x and y > >> parameters to cut a h120 x w90 thumb *from the center > >> of the image* > >> > >> eg: if from problem 1 the result is an image of 120 x > >> 160 then x=35 and y=125 (I think, i told you i suck at > >> maths.. :-D ) > > > > > > This one's even easier. Using the same 1275 x 852 image: > > > > > > 1275 w - 120 w = 1155 (difference in widths) > > > > 1155 / 2 = 577.5 (578 rounded let's say). That's how much > space you'll > > have on either wide width-wise. That'll give you a 120w > "center cut" > > > > Do the same with the height: > > > > 852 - 90 = 762 > > > > 762 / 2 = 381 > > > > > > So your top-left pixel to start cutting would be at 578 x 381. > > > > > > Try it out and let us know how it worked. > > > > -TG > > > > -- > > PHP General Mailing List (http://www.php.net/) > > To unsubscribe, visit: http://www.php.net/unsub.php > > > >