This dialog, opened from the Window menu, allows you take snapshots of the active image window, including the scale bar and other features such as Navigator items drawn on there. The image can be saved at the same size as it is displayed or scaled up to be saved at higher resolution. Snapshots can be saved to TIFF files with various kinds of compression, or to JPEG files. The snapshot is done by creating a buffer of the size needed to contain the scaled image, drawing into that buffer, and saving the buffer. Only the image area is drawn, not the purple background that shows up when an image is smaller than the window. By default, the pixel size will be saved as TIFF resolution information in dots per inch and will usually be detected correctly as a pixel size in IMOD. However, this might be problematic when opening files in other software such as Photoshop. The property 'AddDPItoSnapshots' can be set to 0 to prevent the pixel size from being stored, or to a specific value greater than 1 (e.g., 300) to set the resolution to that DPI value. This property can be set with the script command 'SetProperty'.
Drawing into a buffer is limited to 512 Mpixels (~23Kx23K). A montage larger than this can be drawn at 1:1 zoom because the program draws a series of subareas smaller than this size limit and composes a full image from them. This can take several secondsper subarea, and the STOP button can be used to stop the process. This method is not implemented when a scaling other than 1:1 zoom makes the scaled images too large; in this case the program will suggest that you use 1:1 zoom instead.
Saving a large compressed TIFF snapshot can take many seconds. The snapshot is saved in a background thread unless saving to files in the background is disabled. Other operations can be done during saving, but any file access for reading or saving will cause the program to wait until the background save is finished.
Active window
This line shows the name of the current active image window. Click on the desired window to activate it.
Image scaling
Select No scaling to have the image saved with no scaling, with the same number of pixels in the file as screen pixels. If the image, with its current zoom, is bigger than the window, only the region showing in the window is saved.
Select Scale by and a particular scaling to have the image scaled up to a higher resolution and larger size than the display in the window. Again, only the region of the image showing in the window is saved. Scalings can be 1.5 or integers from 2 to 8.
Select Whole image at 1:1 zoom to save the full image as if it were displayed at a zoom of 1, including anything that would be outside the window at that zoom.
Increase text/line sizes by
With this option on, the program will scale up text sizes, line thicknesses, and the line lengths for crosses by the chosen amount. The default setting is shown as "Scaling", which means that the sizes will be scaled by the same amount as the image is scaled to take the snapshot. Choose this if you plan to view the image at about the same size as it is currently displayed, such as when taking a high-resolution image for publication. In general, choose a scaling that will make the features be an appropriate size for the zoom at which you plan to view the snapshot. With the option off, features are drawn at their normal size regardless of how big the saved image; this is appropriate when you are applying no scaling or very little, or if you plan to examine the saved image at a zoom near 1.
Include features drawn on image
With this option on, the marker point or a drawn line or box, low dose areas, FFT rings, and Navigator features will be drawn in the snapshot. With the option off, only the scale bar and its label will be drawn. (The scale bar can be turned off in the options section of the Image Display Control panel.) The 'SnapshopToFile' script command allows separate control of the drawing of Navigator items and other features.
Save as TIFF or JPEG
Select the type of file to save.
Type of compression in TIFF file
Select whether to use compression in a TIFF file and the type of compression. ZIP and LZW are both loss-less compressions and will generally not reduce file size by a large amount except in special cases. LZW is particularly effective when there are runs of similar pixel values; ZIP is the compression use in PNG files. JPEG compression is the method used in JPEG file and does lose information. However, the compression may be much less effective than when saving a JPEG file in some cases.
JPEG compression quality (%)
The text box and spinner let you specify the compression quality used when saving a JPEG file or a TIFF file with JPEG compression. The default of 80% is usually fine for images but may give unacceptable distortion or dimming of colored features for applications where a good quality image is needed.
Snapshot
Press this button to take the snapshot. A file chooser will open. The first time, you will need to specify a location and filename. Thereafter, the program will increment a number at the end of the filename before the extension or add 1 if there is no number there, so that you can save an automatically numbered sequence of files.