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 Mac’s interface is very nice, what with the menu bar and windows and all, but sometimes don’t you just wish that 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 window’s title bar, you find that you’re losing a little less than 10% of your vertical resolution on a 13” monitor. With JPEGView, you can gain this area back and view images to the full resolution of your screen by choosing the Full Screen option from the View menu (⌘F).
The Full Screen item acts to toggle the view of the current image between a normal window and a full-screen, menubar-less window. In case it’s not obvious which sort of window you’re currently looking at, you can check the View menu to see whether the frontmost 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 (at least if the image is on your menubar monitor). Although you cannot see the menus, all the standard ‚åò-key shortcuts work just fine. In addition, by clicking anywhere inside the full screen window, 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 (though not in full screen windows — see JPEGView Questions & Answers for a full explanation of why not). 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, the selection is cancelled.
Once you’ve 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 (‚åòA) 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. Thus, if you choose this option on an image that is scaled to 50% of its original size, a selection rectangle that is half as wide and half as long as your screen will be created. 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 for effective cropping and zooming.
Cropping and Zooming
Once you’ve made your selection, you are ready to use one of JPEGView’s most powerful features: Crop & Zoom (⌘R), located in the View 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 “Crop” part. The “Zoom” part comes in when JPEGView tries to make this smaller portion of the original image fit on your screen. If you’ve 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. Let’s 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 — and you didn’t have to scroll around helplessly looking for the good bits.
As an added bonus, JPEGView will also let you save JPEG-compressed PICT files in their cropped state. See the section on Saving Images for more details on this. Although their support in other applications is questionable, the beauty of saving cropped PICT images with JPEGView is that you retain the entire original image — nothing is lost! Only the boundaries describing what you see are changed. Thus, JPEGView also supports the Uncrop Image (⌘U) feature, which will remove all cropping from an image and replace it with the complete original. Uncropping works on any cropped image, not only those previously saved to disk with JPEGView.
Changing the scale factors
The last of JPEGView’s special effects is the ability to play with the scaling of images. These options make up the bottom half of the View menu, and all are relatively straightforward to understand and use. 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 image’s 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 you’ve 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 scaling for the image based on the size of its current monitor. This is useful, for instance, if you drag an image from a 13” monitor to a 19” screen and want to expand the image to its natural size on that screen.
