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GIMP: Image and Photo

Manipulation

The GNU Image Manipulation Program (the GIMP) is the open source image and photo manipulator which gives Adobe's very popular and powerful Photoshop a serious run for its money. GIMP is a very powerful tool for editing images and creating impressive graphics. It is one of the highlights of all open source software, and demonstrates the quality that can be achieved through open source development.

This chapter provides a number of recipes for some common tasks using the GIMP. Many excellent books that unleash the full power of the GIMP are available and some are mentioned in Section 35.3.

35.1 Remove Red Eye

Use the lasso selection tool to select the red eye region (zoom in first). Then bring up the Channels dialogue and de-select Green and Blue. Then from the menus choose Desaturate a few times. That should fix it.

35.2 Image Quality

Image resolution (dots per inch or just dpi) is an indication of the quality of an image...........more

It is less important for screen images but more so for printing. Common image resolutions include 72, 120, 300 and 600 dpi (dots per inch). When producing graphics for web pages or for viewing on the screen then 72dpi is generally the more popular resolution (and keep the images to less than about 30K). For scanning and printing, 400dpi is a good quality resolution.

For printing 100dpi is generally exactly 100 dots per inch. On screen however this is not always so, as it depends on the resolution of the monitor (so a 72 pixel wide image on a 17" monitor at 640x480 might come out at about an inch but at 1280x1024 it will be half the size, and so about 144dpi).

When scanning or printing dpi is something that becomes important. For images meant for display on a screen, as in web design it is the pixel dimension that is more important. Consider two images that are both 100x100 pixels, but one is say 100dpi and the another is 300dpi. They will be exactly the same size on your monitor but when printed the first image will be 3 times larger then the second.

The GIF format doesn't store any dpi information-only the pixel dimensions so when the GIMP saves to GIF you "lose" your printer settings! When opening a GIF the resolution will be set to 72dpi.

When designing for screen display of images consider what monitor size will you want to design for (640x480, 800x600, 1024x768, etc). Then ensure your final image is not any larger then your screen. You will also need to take into account that the actual area of your browser is smaller then the screen and so you should keep images as small as possible.

Glade: GUI Builder

Glade is a graphical user interface (GUI) builder for creating applications using the GTK+ and Gnome toolkits. It provides a visual tool (c.f. Visual Basic) to interactively create the GUI on a canvas from components (widgets) provided by the toolkits. Interfaces can be rapidly developed and source code in a variety of languages can be automatically generated. Glade directly generates C source code with support for C++, Ada95, Python, Perl, and Eiffel available within Glade via external tools. Alternatively, LibGlade can be used to dynamically create the user interface directly from the XML data at run time.

As with many Gnome products Glade's native save format is XML (gzip compressed) allowing the interface to be modified, transformed, and viewed by many other XML tools (or even edited manually in your favourite text editor if desired). Independent applications that allow differently structured C source code to be generated directly from the XML data, for example, exist.

In this chapter we begin with an overview of using Glade. We then proceed through the development of a sample Glade application by way of a walk-through that will build the interface. This is followed by walk-throughs that will turn this interface into a fully functional application. These walkthroughs begin with a C implementation and include packaging the application for distribution using the GNU packaging tools (automake, autoconf, and tar). We then walk through the use of the LibGlade library as an alternative for C. Versions of the application in Python and C++ are also presented. We complete this chapter with reference sections covering all aspects of Glade and some basics of the Gtk+ and Gnome toolkits.

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