ColorModels和WritableRasters如何在Java BufferedImages中工作？ [英] How do ColorModels and WritableRasters work in java BufferedImages?

问题描述

在Java中使用 BufferedImage 类时，我通常使用构造函数，其参数为 int width，int height，int type 。但是，对于某些应用程序，我想要一幅图像，该图像将以ARGB顺序使用字节来存储颜色数据，这不能通过这种方式完成（它只有 TYPE_4BYTE_ABGR ）。

When working with the BufferedImage class in Java, I usually use the constructor with parameters int width, int height, int type. For a certain application, though, I wanted an image which would store the color data using bytes in the order ARGB, which can't be done in that way (it has only TYPE_4BYTE_ABGR).

我找到了以下解决方案，效果很好：

I found the following solution, which worked fine:

    WritableRaster raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, width, height, 4, null);
    ColorModel colorModel = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB), new int[]{8,8,8,8}, true, false, ColorModel.TRANSLUCENT, DataBuffer.TYPE_BYTE);
    img = new BufferedImage(colorModel, raster, false, new Hashtable<>());

我不明白为什么这样做？

I don't understand why this works?

尽管-我知道 WritableRaster 是保存图片像素数据的数据结构，但是过去我迷路了。这两个对象（栅格或ColorModel）中的哪一个确定像素数据的顺序为RGBA？以及如何使用（ColorModel，WritableRaster，boolean，HashTable）在BufferedImage的（int，int，int）构造函数中模拟任何类型/ code>构造函数？

Though - I understand that the WritableRaster is the data structure that holds the pixel data of the picture, but past that I am lost. Which of these two objects - the Raster, or the ColorModel - determines that the pixel data is in the order RGBA? And how could I simulate any of the types in BufferedImage's (int, int, int) constructor using the (ColorModel, WritableRaster, boolean, HashTable) constructor?

推荐答案

这是方法

Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, width, height, 4, null);

...指定字节顺序。它隐含地这样做，通过假设4个波段，您希望波段偏移为 0、1、2、3 （对应于RGBA；有关详细信息，请参见源） 。对于RGB颜色空间，波段0 =红色，1 =绿色，2 =蓝色和3 = Alpha。

...that specifies the byte order. It does so implicitly, by assuming for 4 bands, you want the band offsets to be 0, 1, 2, 3 (which corresponds to RGBA; see the source for details). For RGB color space, band 0 = Red, 1 = Green, 2 = Blue and 3 = Alpha.

如果需要不同的顺序，则可以使用其他颜色工厂方法，例如以ARGB顺序创建栅格：

If you wanted a different order, you could have used a different factory method, for instance to create a raster with ARGB order:

Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE, width, height, 
                               width * 4, 4, new int[] {3, 0, 1, 2}, null);

这两种方法都将创建 PixelInterleavedSampleModel 对您来说，正是这个 SampleModel 真正控制了样品顺序。

Both of these methods will create an instance of PixelInterleavedSampleModel for you, and it's this SampleModel that really controls the sample order.

对于 BufferedImage（int，int，int）构造函数可以工作，以及如何做类似的事情，我认为最好的办法就是自己看一下源代码。这基本上是一个很大的 switch 语句，其中对于每个常量 TYPE _ * ，它都会创建一个 WritableRaster 和 ColorModel 与上面的操作类似。

For how the BufferedImage(int, int, int) constructor works, and how you could do similar things, I think the best would be to just look at the source code for yourself. It's basically one big switch statement, where for each constant TYPE_* it creates a WritableRaster and a ColorModel similar to how you do it above.

例如：

ColorModel colorModel = ColorModel.getRGBdefault();
WritableRaster raster = colorModel.createCompatibleWritableRaster(width, height);

new BufferedImage(colorModel, raster, colorModel.isAlpahPremultiplied(), null); 

...将创建类型为 TYPE_INT_ARGB （这种反向查找的实际工作方式有些讨厌，但它的工作方式是... :-））。如果 BufferedImage 中没有相应的类型，则该类型将为 TYPE_CUSTOM （ 0 ）。

...will create an image with type TYPE_INT_ARGB (the way this reverse lookup actually works is somewhat nasty, but it works... :-)). If no corresponding type exists in BufferedImage the type will be TYPE_CUSTOM (0).

这篇关于ColorModels和WritableRasters如何在Java BufferedImages中工作？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！