On 02/16/2012 03:18 PM, Daniel Smith wrote:
> Hey all. I would hope this might get some responses...
> I just today saved my first png file.
> In doing so Gimp came up with a choice box, as to parameters you can choose
> or not:
> Interlacing (Adam7) (whatever that is)
> Save background color
> Save gamma
> Save layer offset
> Save resolution
> Save creation time
> Can anyone tell me which of these options they use?
> What does Adam7 mean?

Hey Daniel,

Interlacing is a technique that enables web browsers to display an
ultra-low-quality version of the whole image, that becomes
progressively clearer while the image is still downloading.  With
modern Internet connection speeds, this is harmless but unnecessary.

The background color, gamma, and layer offset features that are
probably not relevant for your application; I have never found a use
for them myself.  Saving resolution may be useful in some exotic
situations, but generally speaking web browsers will scale any image
to the size specified in the (x)html tag that puts the image on the
page.  Creation time is just the system clock time when you saved
the image, useful for revision control under some circumstances but
probably not yours.

PNG is a lossless format, so unless you are saving a lot of giant
images and run short of time, there is no reason to dial back the
compression from the default "9".

> I am looking to create some web pages with drupal.
> Can anyone tell me their process they use to do
> a similar goal? (With drupal or WP, etc.) What I'm thinking
> is that certain of the settings are compatible or not with
> the blogging engine or not? do you use png or jpeg?, etc.

Generally speaking, any blogging engine that allows you to mess with
the (x)html should not do anything bad to your images.  The server
should just store them, along with the code that enables browsers to
download and display them on the page.  All of the above image
formats should work.

I usually use jpg format for nearly all web images, because
comparable images saved in png normally have larger file sizes.  The
most potentially interesting feature of png is that it saves
transparency, and *nearly* all web browsers now in use understand
how to display png images with transparent areas.  If you need a
transparent background, and you need higher resolution or better
scalability than the gif format provides, png might be your answer. 
Others may know uses for png that I am not aware of, but so far I
have found no use for it in web design.

You will probably be working from a template that specifies the
position and size of some key images, such as a large header image. 
In these instances, build images to that specification.  Other
images can be placed freely in the main content and sidebar areas;
in these instances, again, just make sure that the images you make
fit the space provided.

In re transparency, most of the time you will not need it.  If you
load the page under construction in a web browser and use the
eyedropperin the GIMP foreground/background color tool, you can set
the exact value to make an opaque part of your image match the page
background exactly. 

In other instances, you might need to use transparency for something
like an easy to change custom font text or logo appearing over a
background image.  In these cases, I usually build the image with
the background image included, create a layer that has the text etc.
merged into the background image, then do a selection and invert on
a layer that has the text only, so that I can delete the background
from the text+background layer cleanly.  This gives much better
anti-aliasing than just saving the layer with the text content.

Example:  http://avptampabay.org/demo/

Per usual, there are lots of ways to do these things, and mine may
not be the one you end up using.



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