Making Transparent And Matted Images - Adobe PHOTOSHOP ELEMENTS Manual

Setting optimization options for PNG-24
format
PNG-24 format is suitable for compressing
continuous-tone images. However, PNG-24 files
are often much larger than JPEG files of the same
image. PNG-24 format is recommended only
when working with a continuous-tone image that
includes multilevel transparency. (See "About
PNG-24 format" on page 229.)
To optimize an image in PNG-24 format:
Choose PNG-24 for the optimization format.
1
2 Select Interlaced to create an image that displays
low-resolution versions in a browser while the full
image file is downloading. Interlacing can make
downloading time seem shorter, and assures
viewers that downloading is in progress.
If the image contains transparency, select Trans-
3
parency to preserve transparent pixels as trans-
parent; deselect Transparency to fill fully and
partially transparent pixels with the Matte color.
(See "Making transparent and matted images" on
page 233.)
Making transparent and matted
images
Transparency makes it possible to place a nonrect-
angular graphic object against the background of a
Web page. Background transparency, supported
by GIF and PNG formats, preserves transparent
pixels in the image. These pixels allow the Web
page background to show through in a browser.
ADOBE PHOTOSHOP ELEMENTS
Background matting, supported by GIF, PNG, and
JPEG formats, simulates transparency by filling or
blending transparent pixels with a matte color that
you choose to match the Web page background on
which the image will be placed. Background
matting works better if the Web page background
will be a solid color, and if you know what that
color will be.
The original image must contain transparent
pixels in order for you to create background trans-
parency or background matting in the optimized
image. You can create transparency when you
create a new layer.
Note: You can use the magic eraser tool or the
background eraser tool to easily create transparency
in an image. (See "Using the magic eraser tool" on
page 140 and "Using the background eraser tool" on
page 141.)
Preserving transparency in GIF and PNG
images
GIF format and PNG-8 format support one level
of transparency—pixels can be fully transparent or
fully opaque, but not partially transparent.
PNG-24 format, on the other hand, supports
multilevel transparency, letting you preserve up to
256 levels of transparency in an image.
To preserve background transparency in a GIF or
PNG image:
Open or create an image that contains
1
transparency, and choose File > Save for Web.
In the Save For Web dialog box, select GIF,
2
PNG-8, or PNG-24 as the optimization format.
233
User Guide