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About this book

Since the advent of digital photography, we have been able to post-process our pictures. However, to do it properly, we have to become digital art apprentices. Sebastian Montabone is a computer vision expert who wants us to use our cameras and image processing software to come up with works of art. In this book, he teaches image processing techniques of ascending difficulty based on freely available tools. The book teaches you to use the best tools for the job, and it focuses on the techniques, not the environments or toolchains in which they run. Also in this book, you'll learn about the Canon Hack Development Kit (CHDK), which expands the features of some cameras.

Table of Contents

Chapter 1. Digital Photography

In this book, I will explain how to do these things and more with the help of free software—you don’t have to buy expensive software to achieve these results. After you finish reading this book, you will be able to convert your images into great-looking photos using the software and techniques I describe.

Chapter 2. Digital Images

After reading the previous chapter, you are now able to control your camera so that you can capture the exact type of photograph that you want. When you are out in the field taking photographs, you can already apply the concepts that you have learned so far.

Chapter 3. Geometric Transforms

In the previous chapters, you gained a solid background on photography and digital images. Now is the time for you to start learning how to process your images, and I will start with some of the most common and simple tasks that every photographer has to do: resizing, cropping, rotating, and flipping images. These operations are known as geometric transforms and they are the focus of this chapter. Note that the term transform simply refers to any qualitative change produced in an image. For showing you how to perform these operations, I will use Gimp and ImageMagick, which you already know from the previous chapter.

Chapter 4. Color Transforms

Color is an illusion. What we normally perceive as color is actually a complex interaction between the eye and the brain.

Chapter 5. Filters

It all started with optical filters. For a long time, photographers have been attaching filters to their lenses so that they could have more control on the shots they capture. With the help of these filters, they can make changes to their images and create better photos. There are many types of optical filters, each one for a specific use. Some examples of them are color-correcting filters, infrared filters, neutral density filters, and many more. Once digital photography started, digital filters were created. A digital filter is basically a generic term for referring to a special mathematical operation applied to an image. Similar to optical filters, you can apply many operations to a digital image. Each one of them can produce very different results. Some of these operations are used to increase or decrease the sharpness of the image; others are used to remove unwanted noise in the image. There are many other usages, including artistic effects. A generic term that is commonly used to describe all of these operations is filters. In this chapter, I will show you some of the filters most commonly used in digital photography. The filters that I will show you are Blur, Sharpness, Noise Reduction, and a couple of Artistic filters. But first, I will show you how to select a specific region of the image so that you can apply the filter to it instead of the entire image.

Chapter 6. Photo Retouching

Photo retouching is making small changes to your image so that you can fix some problems it has. From time to time, one can be in a situation where even if you have taken a great photograph, something is wrong about it; suddenly a leaf moved and appeared in the corner of your unique shot; your friend’s eyes appeared glowing red in the image; the metadata, which is the information about your photograph, was lost after processing the image with some editor; and so forth. These are some of the occasions where photo retouching comes into play: removing unwanted objects, red-eye removal, selective colorization, and working with metadata. This chapter explains some of the tools available to obtain these results. Note that I will cover the most commonly used tools for retouching small portions of a photograph, but I’m not going into details about the techniques that some artists use for completely changing a photograph by painting on top of it.

Chapter 7. HDR Imaging

Picture this: You are staring at an incredible landscape. The view is amazing, the sky is clear, and the sun is shining, producing a rich mixture of highlights and shadows. You take as many pictures as you can and then start your trip back after contemplating the landscape once again. After you arrive home and look at your pictures on the computer, you realize that the images do not give justice to what you just saw. It seems to you that the camera, somehow, was not able to capture the richness of the landscape. In some pictures, you have a nice exposure of the darker areas of the landscape, while the bright areas, where the sun was being reflected, look almost white without showing any details. On other pictures, you got a nice exposure of those bright areas, but in those pictures, the darker areas look too black to see the details on them properly.

Chapter 8. Distortion Correction

In photography, there are commonly two different sources of distortion. One of them is produced inside the camera, particularly in the lens. This distortion is called lens distortion. The other is produced by the relative position of the camera and the scene. This distortion is called perspective distortion. In this chapter, I will describe these two sources of distortion and show you how to correct them.

Chapter 9. Panorama Photo Stitching

A panorama is an image that represents a much larger field of view than a regular image. You can use them for many purposes, such as banners, newsletter separators, posters, or web site headers. In many cases, you cannot capture the entire scene in a single shot with a regular camera. One of those cases can be, for example, when you try to take a photograph of a very tall or wide building. In those cases, you can create a panorama by just taking many regular photographs of the scene and then stitch them on your computer to create a single panoramic image. Note that creating a panorama with this method results in an image with larger resolution than a regular shot so you will also be able to make larger prints from it.

Chapter 10. Movie Editing

Today, many digital cameras offer the ability to record videos. Some of them even allow you to record in high-definition. This is very handy since you do not need to carry a completely different device for just creating video clips.

Chapter 11. Canon Hack Development Kit

The Cannon Hack Development Kit (CHDK) is software that enhances the features of some Canon cameras. It is the result of excellent work of many people around the world. The web site for the project contains up-to-date information, a forum, downloads, and a wiki page. You can visit it at http://chdk.wikia.com

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