1. Opening, viewing and saving images

This section of the tutorial introduces you to the Bilko document type you will come across most frequently: Image documents. There are many different types, each distinguished by its file extension - as you can see from the list that appears in the open file dialog ( figure (9K)). The next few pages will introduce you to the main types.

Aim and objectives

This lessons demonstrates how to open and manipulate some of the common image formats. By the end of the lesson you should be able to

• open the different image file types that are supported by Bilko software,
• understand what an image contains, and how to read values from it,
• understand how geophysical values such as temperature is represented by the numerical data making up the image grid,
• use the zoom and reflect functions,
• create and save new images.

Chapter content

1. Opening a raster image - 8-bit image files (BMP,GIF,PCX,TIF)
2. The Bilko image window - resizing, scrolling, using the colour bar
3. The zoom function - enlarging or reducing an image display
4. Examining pixel values - obtaining information from the status bar
5. Selecting subareas - choosing a region from within an image
6. Creating and saving new images
7. Opening flat file images - dealing with binary data grids(BIN)
8. Opening hierarchical data files - self describing files (HDF, NetCDF, N1)
9. Saving high precision images - 16-bit, 32-bit and floating-point data
10. Opening Envisat scenes - 16-bit, 32-bit and floating-point data
11. Summary and conclusions what you should have learnt in this tutorial section

Images used in this chapter

The images for this lesson (below) are usually stored in the folder called tutorial_data Throughout the lesson you can use the links on the right sidebar to get information about them.

• atsr199701.gif' and 'atsr199801.gif
  Images of global sea surface temperature (SST) in January, derived from measurements made by ESA's ATSR instrument in 1997 and 1998.

• amsre_200301v3.bin
  Binary flat file of global SST, (+ 3 atmospheric variables), derived from measurements by NASA's AMSR-E sensor in January 2003.
  

• ATS_10arcmin_DSST_0301.hdf
  Sea surface temperature for January 2003 derived from ESA's AATSR sensor onboard ENVISAT

• ATS_TOA_1C_20040201~.N1
  Level 1 scene of southern Africa recorded by AATSR on Envisat.