Snapper

Contents

Introduction

Snapper is a versatile screen capture program. It allows you to save an area of the screen as a sprite, or in PNG or JPEG format. Paint already has such a 'snap shot' facility, at least for sprites. The reason for having another program to do this job is that some of the most common tasks, like saving the contents of a window or menu, are messy using Paint, which requires the use of an imaginary rectangle and a time delay.

Snapper was originally written by David Pilling, and supplied with his scanning and image processing software suite. With the full agreement and encouragement of David, Chris Johnson has taken on the maintenance and development of Snapper, and the new version is now freely available.

A consequence of this is that all correspondence about Snapper should now be directed to Chris Johnson (Email: chris@chris-johnson.org.uk), and not to David.

Installation

For a new installation, simply drag and drop the Snapper application into the directory of your choice.

If you have a previous copy of Snapper then move the old version of Snapper somewhere safe and replace it with the new version.

Usage

Snapper is run in the usual way by double clicking on its icon. It will install on the icon bar.

The icon bar menu

Info - shows application information, including the version number, and also contains a Web button to check the download site for later releases.

Help... - opens the html help file (this one).

Control - will open the Snapper control window (see below). The control window can more easily be opened by clicking on the icon bar icon with Select.

Save choices - will save the current Snapper configuration. The option to save the configuration is placed on this menu, because it will also save the position and size of the snapper control window and the snap area.

Save choices will save the following details.

• snap mode setting
• show pointer setting
• move pointer setting
• the key combination to trigger a save
• the save method
• the save path
• the fill colour for the area snap
• whether the snap area coordinate window will always open when the snap area is set
• whether the target window will be brought to the front before snapping
• the position and size of the control window
• the position and size of the snap area box
• whether to use the desktop font to label the area top bar
• the default output format (sprite, png, jpeg)
• the jpeg quality setting
• whether to add the /jpg or /png extension to files saved in those formats

These settings are described in detail below.

Quit - will remove the application from the iconbar.

The default control window

The default control window shows 4 buttons that can be used to select the mode in which the program will work.

Screen

In this mode the entire screen area will be captured each time.

Window

In this mode the window under the mouse pointer will be captured. This includes the window title bar and scroll bars. This was the mode used to capture the screen shot of the control window, above.

Contents

In this mode the contents of the window under the mouse will be saved, without any of the window furniture. For example, when this mode is used to capture the control window, this is the result.

Area

In this mode, a box will appear marking an area of the screen. The area inside the box will be saved. The area can be moved or resized by dragging on the sides or corners.

Drag on a corner. Dragging on any of the corners will resize the rectangular area by moving that corner. If the control key is held down while dragging any of the corners, the area will expand or contract symmetrically about the centre point. If the shift key is held down, then dragging any corner will move the whole area rather than change its size.

Drag on a side. Dragging the side of the area will move the area around the screen. If the shift key is held down while dragging, the area will be resized by moving only that side. In addition, double clicking on any side of the area will open the coordinate display window (more details below).

When the area is moved or resized, the snap area will be constrained to the screen boundaries, although to fully include the screen edge, the corresponding border will be just out of view off screen. Note also that the area follows the normal wimp convention for dragging, i.e. dragging with SELECT will bring the area to the top of the window stack, dragging with ADJUST will retain its original position in the window stack.

The size of the area to grab (in pixel) is shown in the top bar of the bounding box. The values update in real time as the box is resized.

If you need even more precise control over the position and size of the snap area, then you can use the coordinate display window (more details below).

Snap button

Finally the 'Snap' button triggers the screen capture. The save can either be

1. via a standard save box
2. directly to a preconfigured directory
3. to the global clipboard
4. immediately filer_run

More details on saving are given below.

Obviously the Snap button is not always of use. For the Window and Contents modes, you would always end up with a picture of the Snapper control window. To get around this, it is also possible to trigger screen capture with a key press. By default this keypress is to hold down the left hand Ctrl and Alt keys.

The full size control window

Toggling the snapper window to full size (click on the top right corner icon) reveals more options, as shown in the window at the right and sections of the window below.

Key trigger

This allows you to set which key press combination will start the screen capture. You need to pick a combination that will not clash with other apps using hotkey combinations, such as Keystroke. You can now use the left and right SHIFT, CTRL, ALT and LOGO keys (some keyboards do not always have both LOGO keys). It should be possible to pick a key combination that does not interact with other software. Note that it is not necessary to choose a two key combination. You can select as many (or as few) keys as you like, although two adjacent keys is probably the best option for normal use.

Pointer

There are two options. Move will remove the pointer from the screen area before capturing the screen. This is useful if you want to capture a menu. With move selected, the menu will appear without the usual inverted selection where the pointer is. Show will display the pointer in its correct position on any captured images. There is further information on the hints page.

Note for MoreDesk users: An option in MoreDesk is to use 'Alt key + mouse moved to edge of screen' to navigate to the next screen. If you have the Snapper option 'Move' set, and the Alt key is one of your trigger keys, then when the pointer is moved to the bottom left of the screen during the grab, and the Alt key is still being held down, MoreDesk will detect this and may change screens! You then end up grabbing an area of the wrong screen.

Fill

This allows you to specify the fill colour for the area window. If the fill is set as Trans (transparent) then everything visible within the area border will be captured. If there is a fill colour set, then only windows in front of the area will appear. The area window follows the usual rules for window order. Dragging it around with adjust will preserve its position in the window stack. Dragging with select will bring it to the front. The fill colour can be chosen by clicking on the menu button to the right of the set colour and then making a selection from the menu. The colours are limited to the standard wimp colours There is further information on the hints page.

Save options

A full description of the options for saving files is given below.

Bring target window to front

If other windows overlay part of the target window then these will be shown when the window is snapped. If this option is selected, then Snapper will bring the target window to the front before snapping, and then return it to the original position in the window stack after the snap.

Hide control window on screen grab

If this is ticked then the control window will be temporarily hidden when a full screen grab is carried out. This only applies to the screen setting, and not to e.g. window, and only to normal desktop operation.

More settings...

Clicking on this button will open the 'More settings' dialogue, shown below.

Options for saving the screen snap

Saves from within the desktop

In the case of saves from within the desktop, there are four ways of completing the snap. The method is set by clicking on the menu button and selecting from the resulting menu, which is shown below. You will need to save choices from the iconbar menu for the new setting to be remembered after Snapper is quit.

Use Save As

A standard SaveAs dialogue will be opened when you click on the Snap button or use the key trigger. You can select the image filetype for the save by selecting the appropriate button in the SaveAs dialogue as shown below. The icon (which should reflect your choice of filetype) may be dragged to a directory viewer to save to disc, or directly to an application that is able to load that type of file. Once a save has been made to disc, then the path and filetype are remembered, so that if subsequent saves are required in the same directory, it is possible to click on the OK button to save immediately. The filename numerical suffix will increment with each save so the previous file will not be overwritten.

Use Save path

When you click on the Snap button or use the key trigger the save path is used directly without opening a SaveAs dialogue, and the file is saved immediately in the designated directory. The filename suffix will increment to prevent previous files being overwritten.

In order to set the Save path to other than the default (which is set to the same directory as that holding the Snapper application), you have three options.

1. Enter the full path manually and press RETURN
2. Click on the menu button just to the right of the save path writable field. This will open a save box. The icon must be dragged into the directory in which you want the images to be saved

   

3. Drag the destination directory from the filer window into the save path writable field

   

Whichever method you use, you will need to save choices from the iconbar menu for the new setting to be remembered after Snapper is quit.

The image file format for direct saves using the Save path is shown in the lower field and is selected by using the popup menu button to the right of the field. The image file types are sprite, draw (a sprite in a drawfile wrapper), PNG or JPEG.

Use clipboard

In this case, when the snap is made, the captured sprite is held in memory, without an actual save being made, and Snapper claims the global clipboard. The snap may then be pasted into another application that supports the global clipboard and will paste sprites. Examples are OvationPro and TechWriter.

When using the clipboard it is only possible to paste as a sprite (or drawfile wrapped sprite). This is due to the png and jpeg library routines used here writing the converted image directly to a file. In addition, very few, if any, RISC OS applications will request the clipboard contents as png or jpeg type.

Filer_Run

With this setting, Snapper will save the snap into the configured save directory (as above for Use Save path), but will then issue a Filer_run command for the file. The snap should then be directly loaded into the configured application for running that image format. The default for sprites will be !Paint. For formats such as PNG, a suitable application must have been booted, so that the run action for the file has been set up.

Capturing the complete desktop screen without the snapper control window being visible
There are two options:

1. The simplest way is to hide the snapper control window behind another window before using the hotkey combination to make the snap. This way you have the full range of save methods and save filetypes available.
2. Make sure that Screen is the mode selected. The control window can then be closed and the capture initiated with the key trigger. In this case it is the module which deals with the save as described in the next section. The snap will immediately be saved into the configured save path directory as a sprite. You cannot change either the save method or filetype.

Capturing the complete desktop screen without even the snapper iconbar icon being visible
This is a modified version of the second option above. Make sure that Screen is the mode selected. The control window can then be closed, and Snapper quit. Again it is the module which deals with the save, which is initiated using the key trigger, and the sprite will be saved into the configured save path directory.

Saves from outside the desktop
If you have a program that does not run in the desktop, but takes over the screen and runs as a single task, then you can only save in one way. By choosing Screen mode, and ensuring that the Snapper control window is closed before leaving the desktop, screen captures can be achieved from outside the desktop, by using the trigger key combination. The configured Save path will be used to save the screen. In this case the screen will always be saved as a sprite.

This full screen save from outside the desktop is implemented by the Snapper module. This is contained in the module Spell (it shares some code). The module supports one *command, viz. Snapper_Key, which is followed by a number formed from one bit for each of the Left and Right Alt, Ctrl, Shift and Logo keys. So Left Alt contributes 1, Right Alt 2, Left Ctrl 4, Right Ctrl 8, and so on up to Right Logo 128. Files will be saved to the system variable <SnapperFile$Dir>. This information should allow the use of the module outside of Snapper.

More information about the save path may be found in the hints/tutorial section.

More settings

Auto show area coordinates

If this option is ticked, then the coordinate display window will be opened every time the area mode is selected. If not ticked, then the area coordinate window will not open when the Area mode is selected, but can be opened at any time by double clicking on the red border of the area (more details below).

Use desktop font

If this option is ticked, Snapper will use the configured desktop font to show the coordinates in the top bar of the area outline. If not ticked, then Snapper will default to using the Homerton font at 12 pt.

Note that Snapper uses the × (multiplication) symbol in the top bar of the area outline. Some fonts do not include a full set of characters. When a desktop font is configured, Snapper checks the 'width' of this character and if it is very close to zero, probably meaning it is absent, it falls back to using lower case x. There may be occasions when a font includes a different character in the position corresponding to the × character in Latin-1. If this is the case, then switch off the desktop font - the ROM based Homerton font will then be used.

Add filetype extension

If this option is ticked, then when saving the snap in either PNG or JPEG format, Snapper will automatically add the /png or /jpg extension to the filename.

JPEG quality

This is the compression factor (and hence quality of image) that will be used when saving the snap in JPEG format. The default setting is 75, but can be set in steps of 5 between 20 and 95, by means of the bump arrows, the lower the quality setting, the poorer the quality of image. Quality settings less than 20 can introduce various artifacts and banding and are not reccomended. Settings above 95 give much less compression. If very high quality is necessary, then use a lossless compression method, ie PNG.

Convert sprite format

Save sprite in RO 3.5 format

ROOL have introduced a new sprite format (newer than the so-called new format introduced with RISC OS 3.5) and recent versions of RISC OS 5 make use of this. In addition, the latest hardware, e.g. IGEPv5 and Titanium, have the red and blue colours in the new sprites interchanged. When you make a screen grab on such hardware, the sprite generated will be in this new format. This may be of no consequence on the hardware being used. However, older hardware/OS versions may not understand the new format. In addition, a lot of older software cannot display or manipulate such sprites, even on the new hardware. Snapper therefore offers the option to convert these newest sprite types to the older RISC OS 3.5 format before saving. The sprites should then be usable on legacy hardware, OS, and software. This option must be ticked for the sprite conversion to occur, otherwise the saved sprite will be in the native format of the hardware and OS version.

Convert 64K to 32K sprite

RISC OS 6 first introduced the 64K colour depth screen mode and sprites. While these can be viewed on RISC OS 5 and 6, they cannot be used on RISC OS 4. If you are saving in the RISC OS 3.5 format, then this option gives you the choice of saving either as a 64K sprite, or as a 32K sprite. When ticked, the 64K sprite will be converted to the 32K version before saving. Remember, if the option Save sprite in RO 3.5 format is not ticked, then the saved sprite will be a 64K sprite in the native format of the hardware and OS version, whatever the setting of Convert 64K to 32K sprite.

To summarise

If the sprites are being converted from RISC OS 5 format to RISC OS 3.5 format then the following will apply.

32-bit 16M colour screen mode

Converted to a 32-bit 16M colour RISC OS 3.5 sprite with the red/blue colours in correct positions

16-bit 64K colour screen mode

Converted either to a 16-bit 64K or 16-bit 32K colour RISC OS 3.5 sprite with the red/blue colours in correct positions

16-bit 32K colour screen mode

Converted to a 16-bit 32K colour RISC OS 3.5 sprite with the red/blue colours in correct positions

16-bit 4K colour screen mode

Converted to a 16-bit 32K colour RISC OS 3.5 sprite with the red/blue colours in correct positions

The area coordinate display window

If the option Auto show area coordinates in the control window is selected, then the coordinate display window will open every time Area mode is selected. It can also be opened at any time by double clicking anywhere on the red border of the snap area.

Shown in this window are the x and y coordinates of the bottom left corner of the snap area, together with the width and height of the area, all values being in pixel. These values are continuously updated as the area is moved or resized by dragging on the red border.

The values can be set by typing in to the writable fields, or by using the bump icons adjacent to the fields. The size/position of the area is updated either as the bump icons are pressed, or when the up arrow, down arrow or return key is pressed. The bump icons follow the usual convention, i.e. holding down the shift or ctrl keys will increase the step size, and using the adjust button will reverse the direction of movement.

Changing the size or position of the snap area using the coordinate display preserves the position of the snap area in the window stack. If you need to bring the snap area to the front then you can use the key press ctrl-F (the coordinate display window must have the input focus, i.e. the caret must be in one of the writable fields for the key to be recognised). In the same way ctrl-B will force the snap area border behind all the other windows.

The coordinate window is always closed when the snap area is removed from the screen. It can be closed at any time the snap area is showing using the close icon in the title bar, and reopened by double clicking on the red border of the snap area.

Contact

All communication about Snapper should now be directed to Chris Johnson (Email:chris@chris-johnson.org.uk). Suggestions for new features are always welcome.

Web sites

David Pilling's web site is at http://www.davidpilling.com/, in particular, the RISC OS section of the site is at http://www.davidpilling.com/riscos.html.

Chris Johnson's web site is at http://www.chris-johnson.org.uk/index.html, with his RISC OS software at http://www.chris-johnson.org.uk/software/index.html.

Screenshots

It goes without saying that all the screen shots in these notes were acquired using Snapper itself, either in window, content or area mode.