Hi,
eulipion2@yahoo.com (2006-07-18 at 0736.55 -0700):

I'm working out of Learning Web Design by Jennifer Niederst, and it uses Photoshop for dealing with graphics. I've instead opted to use GIMP, and I'm wondering if there is an equivalent to "Constrain Proportions" and "Resample Image" options for resizing an image. For example, the book says this:
"Our sweetpea.tif is way too big, so let's size it down. Making sure both the Constrain Proportions and Resample Image boxes are checked, change the resolution to 72 dpi. The resulting image should be 250 pixels wide and 160 pixels high. Click OK."

Now, to do this I went into the Image->Scale Image dialog, changed X- and Y- Resolution to 72 pixels/inch, but the Image Size didn't change. The link box to the right of each of these options was linked. If I didn't know the image was supposed to be 250x160, is there any way to automate this process? What is the equivalent of the two PS options?

As of 2.2 you have to use:

- Scale image for resample on, as it converts a given amount of pixels to another amount (if you change W or H, but not for changes of X or Y alone).

- Print size for resample off, it only changes the magic info that says how many pixels per real unit.

I think in PS you can change all in one go. Yep, by just checking what is editable or not and how the chain lines look, based in http://www.adobepress.com/articles/article.asp?p=433754&seqNum=5&rl=1

In Gimp you have to use both dialogs, Print after Scale, as the X Res in scale is automatic so if you start with a square of 720 pixels @ 72 DPI (10 inches, whatever applies to Width applies to Height) and want 2 inches and 300 DPI (600 pixels) things will readjust in sync... no, wait, it only readjusts if you try to use inches as unit so you type a 2 for Width, but as soon as you type 300 in resolution the 2 becomes 0.48... and later you can type 2 again for Width and all will stay (talk about experimenting with interface). And if you use 50 percent instead of inches for Width, changes in X Res does not change the Width. Whoa, what a set of rules and what a dance over the input boxes! :-/ I think this is getting even more confusing with each version, or at least not better.

If you only want to change the DPI you can also use the Scale dialog if you use Pixels as unit, but I think that would be bad advice (it is what happens, so if you want to remember all the tricks, up to you).

Another day I will try to find the equivalence of Constraint, if there is one and under which rules. I had enough with the text above.

GSR

Quoting Rick Hogg :

Now, to do this I went into the Image->Scale Image dialog, changed X- and Y- Resolution to 72 pixels/inch, but the Image Size didn't change. The link box to the right of each of these options was linked. If I didn't know the image was supposed to be 250x160, is there any way to automate this process? What is the equivalent of the two PS options?

I am not that familiar with the Photoshop paradigm but perhaps Adobe chose to combine into one what the GIMP maintains as separate operations. If you use the GIMP's "Image->Print size...", you can change the DPI setting so that it matches the setting of the intended output device. You would then use "scale image" to size your image to what it what its real-world dimensions should be on that device.

Hopefully, I am not too far off-track on either what you are seeking.

Rick Hogg escribe:

Now, to do this I went into the Image->Scale Image dialog, changed X- and Y- Resolution to 72 pixels/inch, but the Image Size didn't change.

As far as you don't leave the computer, that parameter doesn't make any sense, as you're always working with pixels. That parameter refers to the size of the image once printed, or "how big your pixels will be".

Cordially, Ismael

Ismael Valladolid Torres writes:

Rick Hogg escribe:

Now, to do this I went into the Image->Scale Image dialog, changed X- and Y- Resolution to 72 pixels/inch, but the Image Size didn't change.

As far as you don't leave the computer, that parameter doesn't make any sense, as you're always working with pixels. That parameter refers to the size of the image once printed, or "how big your pixels will be".

A web page might be printed, too. I don't know how browsers behave. It would both make sense to either use the resolution stored in the image or use the resolution they believe the screen has to generate a similar appearance. The latter makes especially sense when web designers don't pay attention to the resolution stored within the image.

Matthias

Matthias Julius escribe:

A web page might be printed, too. I don't know how browsers behave. It would both make sense to either use the resolution stored in the image or use the resolution they believe the screen has to generate a similar appearance. The latter makes especially sense when web designers don't pay attention to the resolution stored within the image.

I suspect they always assume that for a web page a low resolution is enough and their images use to use 72dpi.

I only pay attention to resolution when I'm about to print an image.

Cordially, Ismael