Stitching Photos in Photoshop
This tutorial will illustrate a flexible method with which to stitch together overlapping photos you downloaded from an image hosting website into a seamless panorama.

To download images, right click on the thumbnail and select, Save image as...

Save them all into a new folder called 'photostitch'.

Adobe Photoshop CS+ has a fuction called Photomerge which does this automatically.

00. CS Photomerge
To compile these images with Photomerge,
download them to your computer, and then select:

File > Automate > Photomerge...
Select all the files from the 'photostitch' folder and then press OK.

As this function is quite sophisticated has been designed very simple to use, it is largely self-explanitory. Drag the images from the top bar into the big white box and align them and closely as possible- Photoshop will snap them together and do the rest.

Though if you look closely at a Photomerged panorama, you will notice that the quality of stitching is clumsy, and it has difficulty integrating images with different perspectives.

Thus Photomerge is a great feature for acheiving the gross effect of the panorama, though it fails to transcend an art of stitching, which this tutorial will demonstrate.

01. Import & Align
a) Open all of the images to stitch together in Photoshop.

b) Select the center most image, in this case pan_03.jpg, and double click on the Background layer in the Layers palette, and rename it pan_03.

Renaming the Background layer is key to enable alpha blending with that layer.

Image > Canvas Size...
Width: 600 percent
Height: 150 percent
c) Now increase the canvas size into hugeness.

Since there are five images being merged together horizontally, increase the document width by at least 500% to give some room to play with.

Now select: Window > Arrange > Tile Horizontally

d) Select the Move tool by pressing V, then drag each of the images into the pan_03.jpg document,
and align them in the right order.

e) Rename the layers in the Layers palette to coorospond to their image names.
To rename a layer, double click on it's name.

Order the layers so that the center most layer, pan_03, is on the bottom.
02. Overlap & Rescale
a) Select the layer pan_04 (second from the right), by holding down Ctrl (), and clicking on it.

b) Set the pan_04 layer opacity to 50% (press 5), and move it into place so that it overlaps the pan_03 layer.

Look for a sharp point near the edge of where the images overlap, and align them perfectly. If the alignment is close, a pattern may emerge spiralling from the center point, illustrating the difference in the their rotation.

c) The pattern of alignment projecting from the center indicates a difference in scale, so to increase the size:

Zoom out [ Ctrl () + ] on the document so that it's height is fully visible.

d) Press Ctrl () + T to free transform the layer, and drag the reference point ( ) onto the point where the two images perfectly align.

Holding the Shift key maintains the aspect ratio while scaling with free transform,
and holding down Alt uses the reference point as the central axis.

e) So holding down Alt + Shift, drag one of the corner handles
rescaling the layer to about 105%

  If the the two photos being stitched together are uneven as a result of a camera tilt while taking the photos, now is the time to rotate the image with the reference point set to their perfect point of alignment.

f) Rotate it about   -1.5

Press ENTER to render the free transformation.

03. Mask & Paint
Now it is key to decide what part of each image will be used. These two images have a significant amount of overlap, and some major variations, such as the angle of the stairs, because the camera taking these pictures was rotated.

In this case, the center image (pan_03) shows the full width of the staircase, so it is better to use this one for that portion of the image.

The object to watch for here is the post at the base of the banister- it is the largest perceptable object that the two images share, and will be the point of their transition.

a) Grab the polygonal lasso tool (Shift + L), and draw a selection around the part of pan_04 to keep.

b) Press the Add Layer Mask button on the layers palette to create a mask that reveals only that selection.

c) Set the pan_04 layer opacity to 100% (press 0)

Now if you look at the upper part of the image, the images still do not perfectly align as this camera distorts the incoming light depending on the angle it enters the lens. In the case of most situations this is unavoidable.

There is obvious tiling happening, and a sharp line is visible where the two images border.

The sharp line could have been avoided by feathering ( Ctrl + Alt + D ) the selection before adding a layer mask, but then the tiling would just be a blur.

d) To minimize this tiling effect,
select the Brush Tool (B), and in the Brushes palette:
set the Diameter to about 50px,
and the Hardness to 0%

Ensure that brush Opacity and Flow are both set to 100%

e) Select the layer mask by pressing ( Ctrl ( ) + \ ) or by clicking on the layer's mask thumbnail in the Layers palette.

f) Press D to select White as the foreground color,
and Black as the background color,
and then press X to swap them so Black is foreground.

g) Now painting Black on the layer mask hides pixels, and painting White reveals them. So pressing X to alternate between colors, go all the way down the seem, painting on the layer mask to hide and reveal the image, until they merge without apparent seems.

To reveal any inconsistencies, toggle the layer's visibility.

To toggle seeing the layer mask overlay, press ( Alt + \ ).

Now repeat Steps 2 and 3 until the whole piece is stitched!

by anson vogt | july.27.2005