转换16位图像的选项 [英] Options to Convert 16 bit Image
问题描述
当我以tiff格式打开16位图像时，它以黑色图像形式打开。仅在ImageJ程序中打开16位的tiff图像。但是，它不会在预览中打开。我想知道现在我有什么选择来以比打开ImageJ来查看格式更简单的方式来查看格式，而不会降低分辨率。我应该将其转换为8位格式，但是当格式从16位减少到8位时我不会丢失数据吗？另外，我还在考虑将tiff图像转换为jpeg，但这会导致分辨率降低吗？
when i open a 16 bit image in tiff format, it opens up as a black image. The 16-bit tiff image only opens in the program ImageJ; however, it does not open in Preview. I am wondering what my options are now to view the format in an easier way that does not reduce the resolution than to open ImageJ to view it. Should I convert it to an 8-bit format, but wouldn't I lose data when the format is reduced from 16 to 8 bit? Also, I was thinking about converting the tiff image to jpeg, but would that result in a reduction in resolution?
推荐答案
在不自动缩放的情况下将12位，14位或16位图像加载到ImageJ中时，可能会出现此问题。在这种情况下，即使实际数据值通常跨得多，该显示也将缩放到整个16位范围（0-65535强度值）。例如，在12位相机上，最大可能的强度值为4095，但是0映射为黑色，65535映射为白色，4095最终（线性）映射为非常暗的灰色，人眼几乎看不到
This problem can arise when 12-bit, 14-bit or 16-bit images are loaded into ImageJ without autoscaling. In that case, the display is scaled to the full 16-bit range (0 - 65535 intensity values), even though the actual data values typically span a much smaller range. For example, on a 12-bit camera, the largest possible intensity value is 4095—but with 0 mapped to black and 65535 mapped to white, 4095 ends up (linearly) mapped to a very very dark gray, nearly invisible to the human eye.
您可以通过以下方法解决此问题：单击图像▶调整▶亮度/对比度...，然后单击自动按钮。
You can fix this by clicking on Image ▶ Adjust ▶ Brightness/Contrast... and hitting the Auto button.
您可以通过将鼠标移到图像上，并查看ImageJ主窗口状态栏中区域中的像素探针输出来验证是否存在实际数据。
You can verify whether the actual data is there by moving the mouse over the image, and looking at the pixel probe output in the status bar area of the main ImageJ window.
换句话说，图像实际上不可能全是0值，而是显示范围可能未设置为与数据范围对齐。如果您的图像的强度值范围从从67到520，但存储为16位图像（潜在值介于0到65535之间）时，默认显示范围也是0 =黑色，65535 =白色，并且它们之间的值线性缩放。因此所有这些值（57到520）将显示为黑色。自动缩放时，它将重置显示范围以匹配数据范围，使值67和以下显示为黑色，值520及以上显示为白色，并且介于两者之间的所有内容均线性缩放。
In other words, it is unlikely that your image is actually all 0 values, but rather the display range is probably not set to align with the data range. If your image has intensity values ranging from e.g. 67 to 520, but stored as a 16-bit image (with potential values ranging from 0 to 65535), the default display range is also 0=black, 65535=white, and values in between scaled linearly. So all those values (57 to 520) will appear near black. When you autoscale, it resets the display range to match the data range, making values 67 and below appear black, values 520 and above appear white, and everything in between scaled linearly.
如果您使用 Bio-Formats 插件将图像导入ImageJ，则可以选中 自动缩放选项，以确保动态显示范围缩放自动发生。
If you use the Bio-Formats plugin to import your images into ImageJ, you can check the "Autoscale" option to ensure this dynamic display range scaling happens automatically.
关于是否转换为JPEG：JPEG是一种有损压缩格式，存在其自身的问题。如果您要进行任何定量分析，强烈建议您不要转换为JPEG。有关更多详细信息，请参见斐济Wiki有关JPEG的文章。
As for whether to convert to JPEG: JPEG is a lossy compression format, which has its own problems. If you are going to do any quantitative analysis at all, I strongly advise not converting to JPEG. See the Fiji wiki's article on JPEG for more details.
类似地，如果只想在另一个应用程序中可视化，则转换为8位就可以了，但是对下转换后的图像执行定量分析通常是错误的。请注意，当ImageJ将16位图像转换为8位（使用图像>类型菜单）时，它将烙印您当前在亮度/对比度对话框中设置的显示范围映射，使 apparent 像素值转换为实际 8位像素值。
Similarly, converting to 8-bit is fine if you want to merely visualize in another application, but it would generally be wrong to perform quantitative analysis on the down-converted image. Note that when ImageJ converts a 16-bit image as 8-bit (using the Image > Type menu), it "burns in" whatever display range mapping you currently have set in the Brightness/Contrast dialog, making the apparent pixel values into the actual 8-bit pixel values.
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