Re: zigzag edges

[Steve Kinney <admin@xxxxxxxxxxxxx>]

On 01/04/2012 01:16 AM, vish wrote:
> hi all,
>
> i am new to gimp and could really use some help.
>
> i have pictures of several shirt fabrics which i need to crop. this is easy. however, i need to add an effect that will make the edges appear to be a zigzag shape. see link below. look at the edges of the picture (including the shadow). this is the type of image effect i'm looking for.
>
> http://www.customshop.com/shop/apparel/custom-mens-dress-shirts/custom-dress-shirts.html?pattern=127
>
> does anyone know how to do this? please help if possible.
>
> thanks

Hey vish,

There are several possible approaches but probably the one you want
is to make an image where your fabric fills most or all of one
layer.  Add a layer mask to this layer, and fill the part you don't
want to show - the cut-out area that leaves a zig zag edge - with
black on the mask.

Start with a new image where the base layer is your cloth.  You will
want this to be about twice as wide as the finished image will be,
relative to the texture of the fabric etc. as required.

Making the pattern for the mask can be done lots of ways but I think
I would probably create a new white layer, make sure my foreground &
background colors are black and white, and use the filter at Filters
> Render > Pattern > Checkerboard.  It will take some calculation
and tweaking to get the right size squares for the look you want.

Then go to Layer > Transform > Arbitrary Rotation, and turn the
checkerboard layer 45 degrees.  Now you will need to use the
rectangular selection tool, and use it to select areas of the
checkerboard to fill with white and black, until you end up with a
layer that with a jagged white center where the cloth will be,
surrounded by black where the cloth won't be visible.  

Next, go back to your "cloth" layer, right-click on its thumbnail in
the Layers tab of your dock, and add a layer mask.  To transfer your
modified checkerboard layer, first click on the new layer mask to
make it the current selection.  Then click on the modified
checkerboard, do Edit > Copy (better: control-c), then Edit > Paste
(better: control-v).  Over in the Layers tab, you will see a
"floating selection".  Just click on the Anchor icon and it will
merge down into the mask.

Now click on the eyeball next to the checkerboard layer to turn it
off.  If all went according to plan, you how have an image of a
piece of cloth with a zig zag edge, on a transparent background.

The drop shadow is easy.  Make a duplicate of your cloth layer. 
Select the mask part on the lower of the two duplicate layers, and
do Filters > Blur > Gaussian Blur to fuzz out the edges of the
mask.  Then click on the image part of the same layer, and fill it
with black.  Finally, activate the Move tool in your main toolbox,
and use the arrow keys on your keyboard to move it around until the
shadow is where you want it.

Crop the image, save as .xcf for later tweaking, save as .png or
.gif for a web image with a transparent background.  Or, if this
will be against a known solid color background, go ahead and make a
layer of the said color and put it at the bottom of the stack before
saving.

Example:  http://pilobilus.net/xfer/zigzag-cloth.xcf  Not a
production quality version of what you want, but it illustrates the
principles.

YMMV, I did the process described to make the sample image but I did
not proofread the post very carefully.

:o)

Steve





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