Batch Processing Grayscale

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來自 Duke University 的課程

Java 程序设计：使用软件解题

2655 個評分

Duke University

Java 程序设计：使用软件解题

2655 個評分

課程 1（共 4 門，Specialization Object Oriented Programming in Java）

Building upon Duke’s “Programming and the Web for Beginners” course, you will grow in your ability to be a problem-solver and programmer by writing Java programs. We are excited that you've chosen to learn Java with us! You will soon be able to solve problems that you find interesting and useful by practicing a design process you will learn in this course. Java concepts presented in this course include basic control flow; object-oriented concepts including classes and methods; custom, open-source classes; and a design-implement-debug process that you can continue to leverage as you build your experience and knowledge of programming principles. The custom, open-source classes will provide a consistent application programming interface (API) so that you can write programs that access and transform images, websites, comma separated value (CSV) files and other data files using simple and accessible coding idioms built on the Java Iterable interface. You will learn to design, test, and debug programs and to find and read Java documentation that can serve as the basis for continued study of Java and programming. After completing this course you will be able to: 1. Edit, compile, and run a Java program; 2. Use conditionals and for loops appropriately in a Java program; 3. Use Java API documentation in writing programs. 4. Debug a Java program using the scientific method; 5. Develop a Java method to solve a specific problem; 6. Develop a set of test cases as part of developing a program; 7. Create a class with multiple methods that work together to solve a problem; and 8. Use divide-and-conquer design techniques for a program that uses more than one method.

從本節課中

MiniProject: Baby Names

This module wraps up the course with a mini project that ties together the different practices, skills, and libraries you have gained across the course! Using data on the popularity of different baby names in the United States from the past several decades, you will be able to compare different names’ popularity over time. While the data we have collected for this course is from the United States, we welcome you to share data from other countries in the course discussion forums. Good luck with the mini project!

Batch Grayscale: Converting Many Files2:58

Grayscale Algorithm: Seven Step Approach4:11

Image Iterable in BlueJ: Grayscale5:36

Batch Processing Grayscale3:30

Saving Images with New Names11:14

Batch Grayscale Summary: Converting Many Files1:09

與講師見面

Owen Astrachan
Professor of the Practice
Computer Science
Robert Duvall
Lecturer
Computer Science
Andrew D. Hilton
Associate Professor of the Practice
Electrical and Computer Engineering
Susan H. Rodger
Professor of the Practice
Computer Science

Having written the code to convert one image to a grayscale,

we'd like to go one stop further and convert many images to grayscale.

We've started here with the class we wrote in the previous video in which we

implemented our algorithm in code.

I've added a method at the bottom, select and

convert, which is going to let us select a bunch of files and convert them all.

You've already seen this code before

which iterates over a selection of files and just prints out their name.

Now we're gonna combine these two ideas to give us code which is going to

iterate over a bunch of files and convert them all to gray scale.

So we're going to start with a very similar structure here.

We're going to make a directory resource.

It's going to a new directory resource and we're going to say for

file F in directory resource dot and if you don't remember this name you can

look at the API, or look at the code we did before.

It's going to be selected files.

And what we did last time was we just printed out F.

What we're going to do this time is we're going to convert

the image corresponding to that file to grayscale.

So I want an image resource in file which is going to be a new image resource.

And I'd like to create this from F, this is, make an image by reading in this file.

Then, I would like another ImageResource,

which we're going to get by calling makeGray, the method we wrote before.

Passing in, I called it inFile,

but I really prefer to call it inImage since it's actually an image.

And then the last thing we're gonna do, is just draw this file so

we can see something happening.

So, I'm going to compile this.

And it told me it cannot find the symbol class file.

What we need to do to use file is import java .io.*,

because that's the package in which files are.

Now it compiles fine.

And now I'm gonna go back over here to my main BlueJ window.

I'm going to make a new grayscale converter.

And now I'm gonna click on this and I'm gonna choose select and convert.

And it popped up this dialogue.

And if we navigate through here back to somewhere there are images.

We can now pick some selection of

pictures that we would like to convert each of them to.

And you can see that it went through and converted each of these pictures into

grayscale and drew the resulting image.

I think it's still converting one of them.

The last one was really big.

All right?

So now, we've put those two ideas together.

We've converted any set of images you select.

The next step is going to be to save these images to a file.

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