There are times when the photos we take with great difficulty were skewed; the horizon line should have a straight so it looks uphill (or downhill). There are several things that could cause our picture angle; shoot without a tripod; we forget to pay attention to the viewfinder, or simply because of a hurry. Do not worry, there’s an easy way for straighten your photos using Photoshop, the following:
Step 1: Open your photo in Photoshop and activate the ruler tool from the toolbox, see the picture below for find out the location of the ruler tool
Step 2: Find a benchmark that should be a straight line, click and drag the tool along the ruler of this line from left to right
Step 3: Click Image>> Image Rotation>> Arbitrary.
Dialog box will appear rotate the canvas, you just click OK.
Step 4: Now you have to do the cropping for eliminate the white area that appears. Type C for activate the Crop Tool, then crop as you want, press Enter (Mac: Return) after cropping.