[英]Incorrect grayscale values from Java BufferedImage Raster
I have a grayscale height map , which I created in Photoshop, and I need to pass it to a Java program for processing. 我有一个在Photoshop中创建的灰度高度图 ,需要将其传递给Java程序进行处理。 I am loading it by using the ImageIO.read(...) method and then converting it to grayscale with this code:
我通过使用ImageIO.read(...)方法加载它,然后使用以下代码将其转换为灰度:
BufferedImage map = ImageIO.read(new File(...));
BufferedImage heightMap = new BufferedImage(map.getWidth(), map.getHeight(), BufferedImage.TYPE_BYTE_GRAY);
heightMap.getGraphics().drawImage(map, 0, 0, null);
heightMap.getGraphics().dispose();
In Photoshop, pixel (0,0) has a value of 17. When I use heightMap.getData().getSample(0, 0, 0)
or ((byte[])(heightMap.getRaster().getDataElements(0, 0, null)))[0] & 0xff
, I get a value of 64. 在Photoshop中,像素(0,0)的值为17。当我使用
heightMap.getData().getSample(0, 0, 0)
或((byte[])(heightMap.getRaster().getDataElements(0, 0, null)))[0] & 0xff
,我得到的值是64。
Interestingly, when I run map.getRGB(0, 0)>>16&0xFF
, I also get the value of 64. 有趣的是,当我运行
map.getRGB(0, 0)>>16&0xFF
,我也得到了64的值。
How do I fix this and get a value of 17? 我该如何解决并获得17的值?
Thanks. 谢谢。
The cause of this issue was the file format (PNG). 此问题的原因是文件格式(PNG)。 In Photoshop, I had the canvas mode set to greyscale and 8 bits/channel.
在Photoshop中,我将画布模式设置为灰度和8位/通道。 After completion, I was saving the image/height map as a PNG which caused Java to load the image as type 0 or TYPE_CUSTOM and caused the greyscale conversion to mess up, probably due to transparency.
完成后,我将图像/高度图另存为PNG,这导致Java将图像加载为类型0或TYPE_CUSTOM,并可能由于透明度而导致灰度转换混乱。
Saving the image to JPEG made Java load the image directly into greyscale ( TYPE_BYTE_GRAY ) and both map.getData().getSample(0, 0, 0)
and ((byte[])(map.getRaster().getDataElements(0, 0, null)))[0] & 0xff
returned a value of 13. Not the perfect value, but way better than the 64. 将图像保存为JPEG使得Java将图像直接加载到灰度( TYPE_BYTE_GRAY )中,并且
map.getData().getSample(0, 0, 0)
和((byte[])(map.getRaster().getDataElements(0, 0, null)))[0] & 0xff
返回值13。这不是完美的值,但比64更好。
PS: As expected, this time map.getRGB(0, 0)>>16&0xFF
returned the incorrect value of 64. PS:如预期的那样,这次
map.getRGB(0, 0)>>16&0xFF
返回了错误的值64。
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