hello, i'm making an image which needs to have a certain width and length. problem is that when i use the tool Filters > Decor > Border and add the same exact number of px the Y and X columns, the image does not maintain proportions with the border added. why?it should add the same exact amount of pixels to the x and to y and keep proportions but it doesn't. thanks.

If you need the border inside the canvas then

Select -> All ctrl-A

Edit -> Stroke Selection with the width twice the required border size.

hello, i'm making an image which needs to have a certain width and length. problem is that when i use the tool Filters > Decor > Border and add the same exact number of px the Y and X columns, the image does not maintain proportions with the border added. why?it should add the same exact amount of pixels to the x and to y and keep proportions but it doesn't. thanks.

If you add the same number of pixels to both the width and the height the aspect ratio will change UNLESS the image is square (height = width) - this is a simple consequence of basic arithmetic.

If you want the aspect ratio to be unaltered you will need to add more pixels on the shortest sides of the image than you do on the longest sides - how may more being determined by the aspect ratio of the original image.

For example if the image was 400 x 200 pixels adding a 10 pixel border to all sides would give 420 x 220 - which alters the aspect ratio. Adding 10 pixels each side and 5 pixels top and bottom gives 420 x 210 which preserves the aspect ratio.

i think when adding the border the canvas also expands to contain it, no?
the border is inside the canvas then, right?

Canvas size remains the same, border is inside the canvas.

You are stroking a selection, the width of the stroke is half inside the canvas, hence the need to double the required size.

rich: www.gimp-forum.net

Mattia,

You said:

also, it's not clear to me why 400 x 200 and 420 x 220 is not keeping aspect ratio? the vertical increases exactly the same amount of the horizontal....

It sounds to me like the problem is that you are confusing "same amount" with "same proportion". They are _not_ the same thing.

Increasing 200 to 220 is a proportional increase of 10%.

If you increase 400 by 10%, that becomes 440, _not_ 420!

Jay

On 12/19/2016 03:18 PM, Mattia wrote:

thank you for the help, much appreciated. this will cause the border to look uneven however, isn't there a work around to this?
also, it's not clear to me why 400 x 200 and 420 x 220 is not keeping aspect ratio? the vertical increases exactly the same amount of the horizontal....

If you add the same number of pixels to both the width and the height the aspect ratio will change UNLESS the image is square (height = width) - this is a simple consequence of basic arithmetic.

If you want the aspect ratio to be unaltered you will need to add more pixels on the shortest sides of the image than you do on the longest sides - how may more being determined by the aspect ratio of the original image.

For example if the image was 400 x 200 pixels adding a 10 pixel border to all sides would give 420 x 220 - which alters the aspect ratio. Adding 10 pixels each side and 5 pixels top and bottom gives 420 x 210 which preserves the aspect ratio.

Jay Smith

e-mail: Jay@JaySmith.com  mailto:Jay@JaySmith.com
website: http://www.JaySmith.com

Jay Smith & Associates
P.O. Box 650
Snow Camp, NC  27349  USA

Phone: Int+US+336-376-9991
Toll-Free Phone in US & Canada:
	1-800-447-8267
Fax: Int+US+336-376-6750

also, it's not clear to me why 400 x 200 and 420 x 220 is not keeping aspect ratio? the vertical increases exactly the same amount of the horizontal....

To put it slightly differently you can think of the aspect ratio as being the width divided by the height.

400/200 = 2.0

420/220 = 1.90909 (approximately)

so the aspect ratios are not the same.