Brian's Photo Blog — Article 72
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iPad Photo Editing, Part Two
Thursday 5 April 2012   —   Category: iPad Workflows
This article is a follow-up to iPad Photo Editing, Part One.

When I was processing the photos of the Eugene federal courthouse yesterday — using the new Adobe Photoshop Touch (PT) app on my iPad 2 — I ran into a major problem with the way PT resizes an image. Specifically, when resizing an image down to a smaller size, PT introduces strong aliasing if there are angled lines that are nearly horizontal or vertical.

Take a look at the first photo to the right. As you will see in subsequent versions, those black “dashes” on the face of the main gray part of the building are actually supposed to be solid black lines! You can also see that the lamppost on the right side of the photo has jagged, stair-like edges. The quality of this image is totally unacceptable, rendering it unusable.

In PT, there are no resampling options like there are in the regular Photoshop (PS). When I opened the same photo in PS, and resized it to the same 400 pixels wide, I chose my standards resampling option: “Bicubic Sharper.” As you can see in the second image to the right, it looks a lot better, but still not great.

So I tried all of the other resampling methods: Bicubic Smoother — Bicubic — Bilinear — Nearest Neighbor. Some worked better than others, but all still left some amount of aliasing. This is definitely a difficult image to resize — usually I don’t have nearly this amount of trouble.

Because this problem is caused by thin, sharp-edged lines at a small horizontal or vertical angle, I had the idea of blurring the image slightly, so that the lines would not be so sharp. I applied a Gaussian Blur with a setting of 2 to the image, resized it using the Bicubic Smoother method, and then applied 20%, one pixel sharpen filter. You can see the result in the third photo to the right. There is still a very slight amount of aliasing on some of the lines, but all in all it looks pretty good, and is definitely the best version so far.

Then I had the idea to use the same technique in PT on the iPad. So I re-opened the full-sized photo, applied a Gaussian Blur with a setting of 3, resized it, and then applied a 50% sharpen effect. You can see this new and improved PT version in the fourth image to the right — quite a dramatic improvement over the normal PT resize shown in the first image! Actually, it even looks better than the best version I made in Photoshop!

Yesterday I was getting a bit disenchanted with Photoshop Touch because of this resizing issue, but now, with a bit of creativity and ingenuity, it’s back in my good graces!
Brian's Photo Blog — Article 72
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