如何更改位图的不透明度? [英] How to change a bitmap's opacity?

问题描述

我有一个位图:

Bitmap bitmap = BitmapFactory.decodeFile("some/arbitrary/path/image.jpg");

但我不会向用户显示图像.我希望 alpha 为 100(共 255 个).如果这是不可能的，我可以设置 Bitmap 的不透明度吗?

But I'm not going to display the image to the user. I want the alpha to be 100 (out of 255). If this is not possible, can I set the opacity of the Bitmap?

推荐答案

你也可以试试 BitmapDrawable 而不是 Bitmap.如果这对您有用取决于您使用位图的方式...

You could also try BitmapDrawable instead of Bitmap. If this is useful for you depends on the way you use the bitmap...

编辑

当一位评论者问他如何用 alpha 存储位图时，这里有一些代码:

As a commenter asked how he can store the bitmap with alpha, here is some code:

// lets create a new empty bitmap
Bitmap newBitmap = Bitmap.createBitmap(originalBitmap.getWidth(), originalBitmap.getHeight(), Bitmap.Config.ARGB_8888);
// create a canvas where we can draw on
Canvas canvas = new Canvas(newBitmap);
// create a paint instance with alpha
Paint alphaPaint = new Paint();
alphaPaint.setAlpha(42);
// now lets draw using alphaPaint instance
canvas.drawBitmap(originalBitmap, 0, 0, alphaPaint);

// now lets store the bitmap to a file - the canvas has drawn on the newBitmap, so we can just store that one
// please add stream handling with try/catch blocks
FileOutputStream fos = new FileOutputStream(new File("/awesome/path/to/bitmap.png"));
newBitmap.compress(Bitmap.CompressFormat.PNG, 100, fos);

这篇关于如何更改位图的不透明度?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！