为什么程序读取图像文件后分辨率会变小? [英] Why do resolutions become smaller after a image file be read by program?

问题描述

我遇到一个问题:

我有不同大小的图像文件. (hdpi，xhdpi，xxhdpi，xxxhdpi)

I have images file having different sizes. (hdpi, xhdpi, xxhdpi, xxxhdpi)

当我在hdpi，xhdpi，xxhdpi设备中使用图像文件时，这很好.

When I used the image files in the in the hdpi,xhdpi,xxhdpi devices, it's good.

但是当设备为xxxhdpi时，图像文件的分辨率变小了.

But when the device is xxxhdpi, the resolutions of the image files was became smaller.

我不知道为什么会这样.

I don't know why it had happened.

例如:

我有2台设备，一个设备的分辨率为xxhdpi，另一个为xxxhdpi.

I have 2 devices, one's resolution is xxhdpi, another one is xxxhdpi.

我有2个图像文件，其中一个放在"drawable-xxhdpi"文件夹中，其分辨率为1080x1920.另一个放置在文件夹"drawable-xxxhdpi"中，其分辨率为1440x2560.

And I have 2 image files, one is put in the folder "drawable-xxhdpi", it's resolution is 1080x1920. Another one is put in the folder "drawable-xxxhdpi", it's resolution is 1440x2560.

当我读取图像文件时，出现了问题.

When I read the image files, problem was appeared.

xxhdpi的情况: 原始图片为1080x1920，读取的图片仍为1080x1920.

The case xxhdpi: The original picture is 1080x1920, and image that was read is 1080x1920 still.

xxxhdpi情况: 原始图片为1440x2560，但读取的图像变为1260x2240.

这是我的代码:

DisplayMetrics metrics = new DisplayMetrics();
            getActivity().getWindowManager().getDefaultDisplay().getMetrics(metrics);
            Log.i("SettingCardFragment", String.format("%37s%dx%d",
                    "Screen resolution: ", metrics.widthPixels, metrics.heightPixels));

            Drawable drawable = ContextCompat.getDrawable(getActivity(),R.drawable.background);
            Log.i("SettingCardFragment", String.format("%37s%dx%d",
                    "(Drawable)Background.png resolution: ", drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight()));

            Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.background);
            Log.i("SettingCardFragment", String.format("%37s%dx%d",
                    "(Bitmap)Background.png resolution: ", bitmap.getWidth(), bitmap.getHeight()));

我使用代码检查所读取图片的分辨率.

I use the code to check the resolution of the picture that was read.

然后我在xxhdpi设备中得到了结果:

And I got the result in xxhdpi device:

SettingCardFragment:                   Screen resolution: 1080x1776
SettingCardFragment: (Drawable)Background.png resolution: 1080x1920
SettingCardFragment:   (Bitmap)Background.png resolution: 1080x1920

，然后在xxxhdpi设备中显示结果:

SettingCardFragment:                   Screen resolution: 1440x2392
SettingCardFragment: (Drawable)Background.png resolution: 1260x2240
SettingCardFragment:   (Bitmap)Background.png resolution: 1260x2240

为什么分辨率从1440x2560变为1260x2240?

Why did the resolution became 1260x2240 from 1440x2560?

如果谁知道这一点，请帮助我〜

If who know this, help me please~

推荐答案

我想我明白了.您正在使用密度为3.5的设备(例如Nexus 6p).您可以使用此代码getResources().getDisplayMetrics().density检查浓度.在这类设备中，使用xxxhdpi然后进行缩放.

I think I figured it out. You are using a device with density 3.5 (like the Nexus 6p). You can check the density with this code getResources().getDisplayMetrics().density. In these kind of devices xxxhdpi is used and then scaled.

因此，如果我们进行缩放数学运算-image_size / xxxhdpi_density * device_density，您将获得所看到的尺寸:

So if we do the scaling math - image_size / xxxhdpi_density * device_density you get the dimensions you are seeing:

2560/4 * 3.5 = 2240

2560 / 4 * 3.5 = 2240

1440/4 * 3.5 = 1260

1440 / 4 * 3.5 = 1260

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