Image Exploration Suite


The Image Exploration Suite from Musbury Consultants is a number of desktop RISC OS applications that work together to allow the user to display flat binary (uncompressed) image files from a number of different format files. There is independent control over the aspect ratio, resolution and palette. It was designed specifically to read images in the FITS, PDS and VICAR formats although it is not limited to this. Basically any file can be rendered as an image and so these applications are tools for exploring files rather than a specific image file format reader. Whilst the applications themselves are small some image files can be large and place a high demand on system memory. Usually you need twice asmuch memory as the size of the image file to display and manipulate the image.

Whilst these applications produce grey scale images you are best viewing them in a 16 bit (thousand of colours) or 24 bit (millions of colours) mode. This is because in an 8 bit (256 colours) mode there are only 16 shades of grey that can be displayed. This increases to 64 grey shades in the 16 bit mode and 256 shades in a 24 bit mode. The applications will work in any screen mode but the higher the mode the better they will look.

The software Suite consists of:-
RawRead --- This will read a file and display 8 bit images and its image histogram.
PallMake -- Allows construction of an 8 bit colour palette to use with either RawRead application.
RawRead32 - This will read and display 16 & 32 bit images stored in both unsigned and 2's complement formats.
CompMake -- Takes three grey scale images and constructs a composite colour image.
SpMovie - view a sprite file as a movie.

!RawRead

Clicking on the bar icon brings up the control window. Set the X and Y size in the icons. The offset is the amount to miss out at the start of the file. If there is a header and the offset is not specified there will be a section of rubbish at the top of the picture. The offset can be specified in terms of lines or bytes. If there a discontinuity seen down the image then the offset needs to be specified in bytes. Dragging the image file onto the icon bar icon will bring up an image display window. If the image is not displayed correctly then you can change the X & Y bits or the offset and try again. Often these values can be worked out by reading the header of the image file, this can be done by opening the file in a text editor like !Edit or !Zap. Dragging an image file into the control window will cause RawRead to try and read the header in of the file and set the controls accordingly. Note due to the number of different formats this is not always successful.
The menu on the Image window will allow you to save the image or alter the grey scale. Inverse will produce an inverted grey scale and "maximise contrast" will search the histogram and set the limits of the grey scale to the maximum and minimum values. Note if the offset is not correctly set then some false values may stop this feature from working to its full effect. Dragging a file into the image window will impose a palette on the image.This file can be a palette file made with PallMake or one of a number of image files. RawRead knows where to find the file in the following file types:-
Gif, Sprite, ARN
Memory Usage
Under the menu on the icon bar there are three memory usage options:-
FS-> Memory - File System to Memory, this reads the file into main memory and manipulates it from there. This is the fastest way to work but requires more memory.
FS-> !Scrap - File System to disc, this reads the file into the scrap area on the hard drive and works from that. This requires less memory but is slower, however it is still faster than the next option if using a CD.
Read FS - File system direct, this reads straight off the file system, very much the slowest option if reading a CD but requires the less memory and no free hard disc space.
Read Header option
This can be set in the icon memory so that header is read and the controls adjusted automatically before the image is displayed. It only works for the types of header that RawRead "knows" about. This is most useful with the Mars digital mosaic files.

!PalMake

PalMake allows you to construct 256 colour palette files. It has a small window that displays a palette strip that is the same size as that used in the RawRead applications. The window may be dragged onto the control panel window and the palette and pointers will have correspondence to the image histogram. The arrows represent the set points these can be dragged about. The colour the pointer is set to is displayed in the two boxes. Clicking on these boxes brings up a colour chooser where you can set the colour at that point. This would be exceedingly tedious if it were not for the menu options that create a range of colours from the two set colours. This is done by straight line interpolation in either RGB or HSV colour space. The colour space option changes the intermediate colours chosen. Also you can choose a complete grey scale between the points with black and white to the left and right or a grey wedge where only the colours between the points are changed. By creating short grey palettes like this you can enhance the contrast of the image. Alternatively for a monochrome image colour washes can be created, this is useful for the Venus Magelian images where the images are derived from radar and as such have no colour validity at all. However Venus landing probes have shown a light yellowish wash to a basically monochrome image. Mars is quite similar only it looks red. This creates what is known as a pseudo colour image. Other, more wacky, palettes and effects can be created. Once made, a palette can be saved to disc or dragged directly into a RawRead image display window.

!RawRead32

RawRead32 takes the basic ideas of RawRead and applies it to 16 and 32 bit images. Because these images have many more grey values in them than could possibly be displayed,or perceived on a screen, this application has to map, or bin ranges of image pixel values into each display pixel value. Its controls are similar to RawRead and the user is recommended to first become familiar with that application. RawRead32 has a number of extra controls that are needed because of the extended range of pixels. The 16 / 32 bit buttons are used to determine whether two or four bytes are read to represent a pixel. These bytes can be stored, in the file, with their most significant byte first (MSB) or their least significant byte first (LSB), radio buttons select which method is used to interpret the file. Finally, the number in the file can be represented as an unsigned value or 2's complement value, again buttons choose which way they are interpreted.

The numbers at each end of the histogram represent the image pixel values that correspond to the display values of Black and White. You can type in values yourself, set them from the maximum andminimum found when reading the file or set them by left and right mouse clicks onthe histogram. When in the 16 bit mode these values are the numbers used but in 32 bit mode those numbers are far too big to deal with so in that case hexadecimal are used.

The "re-bin" button will then apply the changes made in the control window without having to re read the image file. Finally the "Mask" value will apply a mask so that only a limited number of bits in the number are used to give the pixel value. This is important for the IRAS images as some of the images are in 32 bit files but only 17 or so bits are significant in any one image. If this were "chased" with the black and white ends of the histogram a percentage down to nine decimal places would be needed for an adequate display, this is very messy to display. The Reset button sets the display limits to their maximum, that is the black value to zero and the white to the maximum of the number of bits combined with the mask value.

!CompMake

This application is designed to make a composite colour image from three grey scale sprites. There are no colour cameras in space, all probes use monochrome cameras. However, colour images are available because many missions have several filters that can be put in front of the imaging device. Sometimes these filters are in the infra red or ultra violet regions but there are usually some in the visible region as well. For more details see the documentation of specific missions.
!CompMake is extremely easy to use, click on the icon bar to reveal the control window. Drag the sprites you want to use into the appropriate colour section and choose 'make' from the menu. There are in fact two types of make command. The first 'make no pal'just uses the values in the sprite file and the second 'make pal' uses the palette in each sprite as a look up table for the actual pixel values to determine the value to use to make the colour composite image. All the sprites used must be of the 256 colours type with a palette and they mush have identical sizes, if your sprites do not conform to this then use !ChangeFSI to convert them. The output image produced is a 24 bit colour sprite and can be saved to disc. While the sprites are loaded alternative palettes can be loaded by dropping them onto the appropriate image. By using different palettes you can alter the colour balance, brightness and contrast.

!SpMovie

This simple application will show in rapid succession a sequence of sprites held in a single file. In other words allow you to view a movie who's frames are contained in a single sprites. The sprites in the file have to have to be named a three digit number from 000 to 999. Control over frame rate and looping is provided.