There is a powerful command-line way of putting transparency into bitmaps, using Imagemagick's convert utility. But if you don't want to install Leopard, here are some alternatives. So with Keynote, I can't leverage the fruits of my labor for a web page, where transparent GIF or PNG images are often desirable.īecause of this, I'm led to the question: can we do the same kind of thing outside of Keynote to retain more flexibility for later use? With the new Leopard operating system, the answer to this question is: Preview.app (using pretty much the same functionality as described here). The only problem is: exporting the result as a transparent image for use in other applications doesn't seem to be possible. It takes a bit of experimentation to achieve the desired appearance, but this is definitely a slick and simple way of getting bitmaps to behave "transparently". In this example, the combination of masking and Alpha effect allows to make the background behind the tiger disappear. Here is a screenshot of the tool in action: The new Keynote '08 (and similarly the companion product, Pages) has added this feature in the form of an "Alpha" tool that makes creating transparent backgrounds very easy. In fact, many of the neat tricks that one can play with bitmaps are based on the ability to make parts of an image transparent. While iPhoto has many nice features for processing photos, it is certainly not a Photoshop replacement. That's not just true for photos (probably the most common application, this is the reason for the "Photo" in "Photoshop"), but also for many types of numerical simulations. One is described on another page addressing graphics size issues another reason is that sometimes your original graphic comes as a bitmap. Do we really need bitmap graphics? The answer is yes for several reasons. It's ironic: with Quartz, the Mac user interface offers a high-quality vector oriented (PDF) graphics system, but I still find myself using ancient techniques for tasks that don't involve vector graphics, i.e., for manipulation of bitmaps.
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