Special Effects

JPEGView provides a small number of useful on-screen manipulation tools that allow you to adjust the scaling factor of the active image, to perform cropping and zooming, or to make use of the full area of your monitor.  All these features are described in detail below.


The wonders of full screen windows

The MacintoshÕs interface is very nice, what with the menu bar and windows and all, but sometimes donÕt you just wish that a 640x480 image could be displayed in full on your 640x480 display?  When you account for the height of the menu bar plus the height of the windowÕs title bar, you find that youÕre losing a little less than 10% of your vertical resolution on a 13Ó monitor.  (If the windows had scroll bars, youÕd be losing even more!)  With JPEGView, you can gain this area back and view images to the full resolution of your screen simply by choosing the Full Screen option from the View menu (F).

The Full Screen menu item acts to toggle the view of the current image between a normal window and a full-screen, menubar-less window.  In case itÕs not obvious which sort of window youÕre currently looking at, you can check the View menu to see whether the active window is in a full screen window by looking for the checkmark next to this menu item.

When a full screen window is in front, the menubar is hidden from view (this is, assuming the image window is on your menubar monitor).  Although you cannot see the menus, all the standard -key shortcuts work just fine.  In addition, by clicking anywhere inside the full screen window (but outside the current selection, if there is one), you can bring the menubar forward and access the menus in the usual manner.  A second click inside the window will put the menubar away again.  Several other actions can also force the menubar back to the front, including: closing the full screen window; selecting a normal (non-full-screen) window; and switching to another application.


Selecting portions of an image in JPEGView

You may have noticed that when you move the mouse pointer inside the window of the active image, the pointer changes to a crosshair.  In JPEGView, as in most graphics applications, you can select an area of the active image by clicking in the image, dragging a rectangle around the desired area, and then releasing the mouse button to make the selection final.  Once a selection is made, an animated dashed rectangle is displayed around the selected area.  If you select an area less than 16 pixels in one direction,  or simply click without dragging, the selection is canceled.

Once youÕve made your selection, moving the mouse pointer around some move reveals yet another cursor: the hand cursor.  When the mouse pointer lies within the selection rectangle, the pointer becomes a hand to indicate that you can drag the selection area anywhere within the image while preserving its original size.  Note that in order to define a new selection rectangle, you must begin by clicking outside of the original rectangle; otherwise, JPEGView will think you want to drag the original selection around rather than begin a new selection.  Use the cursor shape as your guide: if it is a crosshair, clicking will produce a new selection; if it is a hand, clicking will drag the current selection.

Another intriguing option for making a selection is to use the Select Screen Area (A) option under the Edit menu.  This creates a selection rectangle in the middle of the active image that is exactly the proportions of the monitor that image is displayed on, scaled in the same way as the image.  That is, the selection that is created represents the area of the image you could view if the image were displayed unscaled on your screen.  Once created, this selection rectangle can be dragged about the image like any normal selection.  If this concept seems unclear, read on into the next section to find out how this can be used in conjunction with cropping and zooming to form a very powerful tool for examining images in more detail.

After selecting a portion of the image, you are free to copy it to the clipboard, assuming you have enough memory available to do so.  To give it a try, choose Copy (C) from the Edit menu.  Because JPEGView often deals with very large images, it is easily possible that you will run out of memory during the copy operation; if this happens, you are probably best off copying the image in pieces and reassembling them by hand at the other end.  Also note that if no selection is active, choosing Copy will attempt to copy the entire image.

Similarly, on a drag-aware system, you can drag the selected portion of the image outside of its window and into another application which supports dropping pictures.  Because JPEGView already allows you to drag selections within windows, this operates a little strangely: when the mouse pointer is displayed as a hand, you can drag the image anywhere within the image itself.  However, once you drag the mouse pointer outside the bounds of the window, you will begin the drag-and-drop operation.  At this point, the original selection is remembered, even if there was no target for the drop.


Cropping and Zooming

Once youÕve made your selection, you are ready to use one of JPEGViewÕs most powerful features: Crop & Zoom (R), located in the Edit menu.  This option takes the area of the image that you have selected and creates a new window containing only that portion of the image.  That takes care of the ÒCropÓ part.  The ÒZoomÓ part comes in when JPEGView tries to make this smaller portion of the original image fit on your screen.  If youÕve selected an area in the original that will fit unscaled on your screen, then it is displayed as such.  If the cropped area is still too large, it is scaled to fit on your screen at the maximum size possible.

The usefulness of this feature becomes apparent when used in conjunction with the Select Screen Area option.  LetÕs say you long for the good old days, when scroll bars were in vogue and you could use your whole screen to look at the minute details in your images without having to see the image scaled down to 50% or whatever.  Well, you can still do that!  Just Select Screen Area on your image, drag the selection over the area you wish to examine, and then Crop & Zoom.  The area you chose will expand to fill up your screen exactly Ñ and you didnÕt have to scroll around helplessly looking for the good bits.

Once youÕve cropped an image, you can always return to the original full-size image by choosing Uncrop Image (U), again in the Edit menu, which will remove all cropping from an image and replace it with the complete original.


Changing the scale factors

The last of JPEGViewÕs special effects is the ability to play with the on-screen scaling of images.  This can be accomplished in one of two ways: either by hand, by dragging the lower-right corner of the image; or automatically, by using the commands at the bottom of the View menu.  The former technique is probably the more intuitive of the two.

If you move your mouse pointer down into the bottom-right corner of the active image, you will notice that the cursor takes on yet another shape: that of a resizing box, which youÕre used to seeing in the bottom-right corner of windows in most other applications.  Clicking and dragging the mouse while the cursor is thusly shaped will allow you to change the size of the current image.  By default, the new size of the image is constrained to have the same ratio of height to width as the original; however, you can remove this restriction by holding down any of the modifier keys (Shift, Control, Option, or ).

Your other options for adjusting an imageÕs onscreen size are accessible from the bottom half of the View menu, and all are relatively straightforward.  You can double or halve the size of the current image with the Double Size (D) and Halve Size (H) menu items, respectively.  Or you can force the image to expand to its maximum size on the current monitor with the Maximum Size (M) item; the zoom box in the upper right-hand corner of an imageÕs window will do this trick as well.

For more precise scaling, you can increment and decrement the scale factor in steps of 10% using the Shrink by 10% ([) and Expand by 10% (]) options.  And when youÕve finished playing with scale factors, you can select the Normal Size (L) option to return the image to 100%.

Finally, for those with multiple monitor systems, there is the Resize to Screen (E) command, which will recompute the standard scaling for the image based on the size of its current monitor.  This is useful, for instance, if you drag an image from a 13Ó monitor to a 19Ó screen and want to expand the image to its natural size on that screen.