Lesson: Working with Images课程：使用图像

As you have already learned from the Images lesson, Images are described by a width and a height, measured in pixels, and have a coordinate system that is independent of the drawing surface.正如您已经从图像课程中了解到的，Image以宽度和高度（以像素为单位）进行描述，并且具有独立于图形表面的坐标系。

There are a number of common tasks when working with images.处理图像时有许多常见任务。

• Loading an external GIF, PNG JPEG image format file into the internal image representation used by Java 2D.将外部GIF、PNG JPEG图像格式文件加载到Java 2D使用的内部图像表示中。
• Directly creating a Java 2D image and rendering to it.直接创建Java 2D图像并对其进行渲染。
• Drawing the contents of a Java 2D image on to a drawing surface.将Java 2D图像的内容绘制到绘图表面。
• Saving the contents of a Java 2D image to an external GIF, PNG, or JPEG image file.将Java 2D图像的内容保存到外部GIF、PNG或JPEG图像文件。

This lesson teaches you the basics of loading, displaying, and saving images.本课程将向您介绍加载、显示和保存图像的基本知识。

The are two main classes that you must learn about to work with images:要使用图像，您必须学习以下两个主要类：

• The java.awt.Image class is the superclass that represents graphical images as rectangular arrays of pixels.java.awt.Image类是将图形图像表示为像素矩形数组的超类。
• The java.awt.image.BufferedImage class, which extends the Image class to allow the application to operate directly with image data (for example, retrieving or setting up the pixel color). java.awt.image.BufferedImage类，它扩展了Image类，允许应用程序直接使用图像数据进行操作（例如，检索或设置像素颜色）。Applications can directly construct instances of this class.应用程序可以直接构造此类的实例。

The BufferedImage class is a cornerstone of the Java 2D immediate-mode imaging API. BuffereImage类是Java2D即时模式成像API的基石。It manages the image in memory and provides methods for storing, interpreting, and obtaining pixel data. 它管理内存中的图像，并提供存储、解释和获取像素数据的方法。Since BufferedImage is a subclass of Image it can be rendered by the Graphics and Graphics2D methods that accept an Image parameter.由于BuffereImage是Image的一个子类，因此可以通过接受Image参数的Graphics和Graphics2D方法进行渲染。

A BufferedImage is essentially an Image with an accessible data buffer. BuffereImage本质上是具有可访问数据缓冲区的Image。It is therefore more efficient to work directly with BufferedImage. 因此，直接使用BuffereImage更有效。A BufferedImage has a ColorModel and a Raster of image data. BuffereImage具有ColorModel和图像数据光栅。The ColorModel provides a color interpretation of the image's pixel data.ColorModel提供图像像素数据的颜色解释。

The Raster performs the following functions:光栅执行以下功能：

• Represents the rectangular coordinates of the image表示图像的直角坐标
• Maintains image data in memory在内存中维护图像数据
• Provides a mechanism for creating multiple subimages from a single image data buffer提供从单个图像数据缓冲区创建多个子图像的机制
• Provides methods for accessing specific pixels within the image提供访问图像中特定像素的方法

The basic operations with images are represented in the following sections:以下部分介绍了图像的基本操作：

Reading/Loading an image读取/加载图像

This section explains how to load an image from an external image format into a Java application using the Image I/O API本节介绍如何使用图像I/O API将图像从外部图像格式加载到Java应用程序中

Drawing an image画图

This section teaches how to display images using the drawImage method of the Graphics and Graphics2D classes.本节介绍如何使用Graphics和Graphics2D类的drawImage方法显示图像。

Creating and drawing To an image创建和绘制图像

This section describes how to create an image and how to use the image itself as a drawing surface.本节介绍如何创建图像以及如何将图像本身用作绘图曲面。

Writing/saving an image写入/保存图像

This section explains how to save created images in an appropriate format.本节介绍如何以适当的格式保存创建的图像。