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Trail: 2D Graphics
Lesson: Working with Images
Working with Images
Reading/Loading an Image
Drawing an Image
Creating and Drawing to an Image
Writing/Saving an Image
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Writing/Saving an Image

> This lesson started with an explanation for using the `javax.imageio` package, to load images from an external image format into Java 2D™'s internal `BufferedImage` format. Then it explains how to use the `Graphics.drawImage()` to draw that image, with optional filtering.

> The final stage is saving a `BufferedImage` object into an external image format. This may be an image that was originally loaded by the `Image I/O` class from an external image format and perhaps modified using the Java 2D APIs, or it may be one that was created by Java 2D.

> The `Image I/O` class provides a simple way to save images in a variety of image formats in the following example:

>     static boolean ImageIO.write(RenderedImage im,
>                                  String formatName,
>                                  File output) throws IOException

> > Note: the `BufferedImage` is a subclass of `RenderedImage`

> .

> The `formatName` parameter selects the image format in which to save the `BufferedImage`.

>         try {
>             BufferedImage bi = getMyImage(); // retrieve image
>             File outputfile = new File("saved.png");
>             ImageIO.write(bi, "png", outputfile);
>         } catch (IOException e)
>         }

> The `ImageIO.write` method calls the code that implements PNG writing a “PNG writer plug-in”. The term plug-in is used since `Image I/O` is extensible and can support a wide range of formats.

> But the following standard image format plugins : JPEG, PNG, GIF, BMP and WBMP are always be present.

> Each image format has its advantages and disadvantages:

> | Plus | Minus
> GIF | Supports animation, and transparent pixels | Supports only 256 colors and no translucency
> PNG | Better alternative than GIF or JPG for high colour lossless images, supports translucency | Doesn't support animation
> JPG | Great for photographic images | Loss of compression, not good for text, screenshots, or any application where the original image must be preserved exactly

> For most applications it is sufficient to use one of these standard plugins. They have the advantage of being readily available. The `Image I/O` class provides a way to plug in support for additional formats which can be used, and many such plug-ins exist. If you are interested in what file formats are available to load or save in your system, you may use the `getReaderFormatNames` and `getWriterFormatNames` methods of the `ImageIO` class. These methods return an array of strings listing all of the formats supported in this JRE.

>     String writerNames[] = ImageIO.getWriterFormatNames();

> The returned array of names will include any additional plug-ins that are installed and any of these names may be used as a format name to select an image writer. The following code example is a simple version of a complete image edit/touch up program which uses a revised version of the `ImageDrawingApplet.java` sample program which can be used as follows :

> - An image is first loaded via Image I/O
> - The user selects a filter from the drop down list and a new updated image is drawn
> - The user selects a save format from the drop down list
> - Next a file chooser appears and the user selects where to save the image
> - The modified image can now be viewed by other desktop applications

> The complete code of this example is represented in `SaveImage.java`.

> In this lesson you have learned just the basics of `Image I/O`, which provides extensive support for writing images, including working directly with an `ImageWriter` plug-in to achieve finer control over the encoding process. ImageIO can write multiple images, image metadata, and determine quality vs. size tradeoffs. For more information see Java Image I/O API Guide.

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