Android 位图 getPixel 取决于密度？

发布于 2024-12-12 04:20:33 字数 501 浏览 0 评论 0原文

正确的代码。鉴于

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId);
Drawable drawable = getResources().getDrawable(resId);

我得到的

bitmap.getWidth() == drawable.getIntrinsicWidth() == 9

实际图像是 6x6 像素。关键是密度为 240，因此比例为 1.5 到 DENSITY_DEFAULT = 160。这本身并不是一个问题，但 bitmap.getPixel(x, y); 也适用于放大的尺寸。

设置位图的密度似乎没有什么区别。我应该如何查询图像中真实位置的像素？我宁愿不将所有东西除以密度（通常甚至不可能）。

谢谢

原文

Right to the code. Given

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId);
Drawable drawable = getResources().getDrawable(resId);

I get

bitmap.getWidth() == drawable.getIntrinsicWidth() == 9

though the actual image is 6x6 pixels. The point is that the density is 240, thus the scale is 1.5 to the DENSITY_DEFAULT = 160. That would not be such an issue itself, but bitmap.getPixel(x, y); does also work with the enlarged dimensions.

Settings bitmap's density seems to make no difference. How should I query the image for pixel at real position? I would rather not divide everything by the density (ofttimes not even possible).

Thanks

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君勿笑 2024-12-19 04:20:33

首先对这里发生的事情发表一些评论。你得到的Bitmap实际上是重新采样的；它的像素数据适用于 9x9 图像。 bitmap.getWidth() 方法不受调用 bitmap.setDensity() 的影响。

要加载位图，同时防止 Android 框架为您重新采样，请创建一个 BitmapFactory.Options 实例并设置 inScaled 为 false，然后将其传递给decodeResource()：

BitmapFactory.Options options = new BitmapFactory.Options();
options.inScaled = false;
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId, options);
// Now bitmap.getWidth() == 6

请注意，它是 UI 中使用的重新采样版本（除非您明确解决该问题），因此如果您想对 UI 中绘制的位图执行 bitmap.getPixel(x,y); 操作，则不应使用 inScaled = false。

First a few comments on what's happening here. The Bitmap you get is actually resampled; its pixel data is for a 9x9 image. The method bitmap.getWidth() is not affected by calls to bitmap.setDensity().

To load the Bitmap while preventing the Android framework from resampling it for you, create a BitmapFactory.Options instance and set inScaled to false, then pass this to decodeResource():

BitmapFactory.Options options = new BitmapFactory.Options();
options.inScaled = false;
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), resId, options);
// Now bitmap.getWidth() == 6

Note that it is the resampled version that is used in the UI (unless you explicitly work around that), so if you want to do bitmap.getPixel(x,y); on the Bitmap that is drawn in the UI, you should not make use of inScaled = false.

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