图像 DPI 解释
尝试编写 DPI 的定义让我想到：
DPI（点）、PPI（点）、LPI（线）都指的是同一概念，以下简称为 DPI。
DPI 是与设备相关的测量。 它说：“这是该设备的分辨率。”
基于矢量的文件不依赖于任何一个 DPI（它们会扩展和收缩以符合特定的分辨率）。
当基于矢量的文件渲染为基于“位图”的格式 - （bmp、png、tiff、jpg）等时......该“位图”文件以特定 DPI 创建，用于在“条带”或“条带”上打印（或显示）以特定 DPI 输出的基于“扫描线”的设备。
现在，有些人会认为 DPI 不存在于基于“位图”的文件中。
我正在寻找 DPI 的定义以及如何或为何将其视为不存在于位图图像中？
Attempting to write a definition of DPI has lead me to:
DPI (dots), PPI (points), LPI (lines) all refer to the same concept hereafter referred to as DPI.
DPI is a device dependent measurement. It says, "This is the resolution of this device."
Vector based files are not tied to any one DPI (they expand and contract to conform to a certain resolution).
When that vector based file is rendered to a "bitmap" based format - (bmp, png, tiff, jpg) etc... that "bitmapped" file is created at a certain DPI for printing (or display) on "banding" or "scanline" based devices that output at that specific DPI.
Now, some would argue that DPI does not exist in "bitmapped" based files.
I'm looking for a definition of DPI and how or why it would be considered to not exist in a bitmapped image?
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由于位图图像没有物理尺寸，因此也没有 dpi。 如果您有一种对物理尺寸进行建模的文件格式，则可以拥有（建模的）dpi。
您可能想要区分可寻址性和覆盖区域。 如果一个点不是正方形而是圆形，则覆盖的面积更大。
顺便说一句，LPI 是一个不同但相关的概念。 600 DPI 打印机的 100 LPI 屏幕意味着有 6*6 像素的正方形可用于创建 37 种不同的灰度级（旋转 0 度）。
Because a bitmapped image has no physical size, it has no dpi. If you have a file format where physical size is modeled, you can have a (modeled) dpi.
You might want to make a distinction between addressability and covered area. If a dot is not square but a circle, the covered area is larger.
b.t.w. LPI is a different but related concept. A 100 LPI screen for a 600 DPI printer means there are squares of 6*6 pixels available to create 37 different levels of gray (with a 0 degree rotation).
某些文件格式将包含 DPI 值，但在大多数情况下可以忽略它。 您关心的是像素尺寸与显示或打印尺寸的比率。 较低的级别通常会导致图像更加模糊。
Certain file formats will contain a DPI value, but it can be ignored for most purposes. What you care about is the ratio of the size in pixels over the size you're displaying or printing. Lower levels generally result in a blurrier picture.
位图图像将指定每个点，并将 DPI 和渲染留给系统的其他部分。 我可以用投影仪在墙上画一张十六乘十六的位图，并声称每英寸有一个点。 更高级的文件格式将指定如何渲染它们，因为它们关心它们的外观。
A bitmapped image would specify each dot, and leave the DPI and therefore the rendering up to some other part of the system. I could draw a sixteen by sixteen bitmap up on the wall with a projector and claim im getting one dot per inch. More advanced file formats will specify how to render them because they care how they look.
如果位图图像指定了 DPI，并且我们还知道显示器/打印机的 DPI，则我们可以按“预期”打印/显示它。
我认为人们应该少考虑 DPI，而更多地考虑以厘米/英寸为单位的预期尺寸。 DPI 的一个好处是它可以让我们衡量输出的效果。
If the bitmap image has it's DPI specified we can print/display it as "intended" if we also know the DPI of the display/printer.
I think one should think less about DPI and more about the intended size in cm/inch. One good thing about DPI is that it can give us a measurement of how good the output will look.