png的ppi很奇怪 [英] Very strange ppi of png

问题描述

我有一些png文件，它们的ppi是300.

I have some png files, and their ppi were 300.

现在我将ppi更改为72，但是图片的大小甚至更大了！

Now I've change the ppi to 72, but the size of the pictures even became larger!

例如，a.png为190k，300ppi，

For example, a.png was 190k, 300ppi,

现在它变为400 + k，72ppi，并且始终为320 * 460，

now it becomes 400+k, 72ppi, and it is always 320*460,

怎么回事，我该怎么办?

what's happening, how should I do?

我本意是减小图片的尺寸.

I was meant to reduce the pictures's size..

推荐答案

ppi代表每英寸像素".

ppi stands for 'pixels per inch'.

图像大小的等式为NoOfPixels = NoOfInches * PixelsPerInch

或NoOfInches = NoOfPixels/PixelsPerInch

因此，降低ppi会增加图像的物理"尺寸.

So reducing the ppi will increase the 'physical' size of the image.

要减小图像的大小，您需要将更多像素压缩到物理"空间的每个图像中，因此请增加ppi

To reduce the size of the image you need to squash more pixels into each image of 'physical' space, so increase the ppi

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