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Open an image in Photoshop. Open the Layers panel. Invert the image. Arrange the inverted layer. Toggle the inverted layer on and off. Try working with the inverted and non-inverted image side-by-side.

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Make sure that the photo lends itself to color inversion. The change will be most dramatic if the image is very dark or very light. Understand that the inversion will replace each color with its corresponding opposite: the brightness value of each pixel is converted to the inverse value on the 256-step color-values scale. Think about whether the photo will be more or less powerful, once inverted. If you aren't sure, it can't hurt to try! Open the "Window" menu, then choose "Layers" to reveal the Layers panel if you can't already see it. Remember; you are not actually changing the colors of the original image file – you are creating a color-inverted layer on top of the base.  If you want to invert the colors in a specific section of the image, use the selection tools—Marquee, Lasso and Magic Wand—to mark out the part that you wish to invert. If you want to invert the colors across the entire image, then you don't need an active selection.  If you're inverting a complex composition, you can add a new layer at the top of the layer stack. Then, press ⇧ Shift+Ctrl+E to create a merged version of your entire composite without changing the deeper layers. Click on the unlabeled "Create New Fill or Adjustment Layer" button at the bottom of the Layers panel; you can find the correct button by hovering over the options. Choose "Invert" from the drop-down menu that appears. Photoshop adds an "Invert Adjustment" layer to your layer stack immediately above either the topmost layer or the layer that was active when you added the adjustment. If you made a selection before adding the adjustment, Photoshop builds a layer mask for the Invert layer. The program inverts the colors in the area that you selected. Drag the Invert layer up or down the layer stack to a new position. Any given layer only acts upon the layers below it, so the inversion's position in the layer stack determines its impact on your file. Shift-click on the layer mask applied to your Invert adjustment layer to disable the mask and apply the adjustment to your entire file. Click on the layer mask icon to enable the adjustment again. Turn off the eyeball indicator at the left edge of the Invert layer listing to disable the adjustment itself. After inverting an image, select Create New Snapshot. Keep each image open in a separate tab. This way, you can work with both the original image and the inverted image.