Android - 保存的图像中存在噪点
我的 Android 应用程序加载图像，进行一些处理并将处理后的图像保存在 SD 卡上。我将临时文件保存到 SD 卡而不是使用缓冲区。例如，读取背景、滚动图像、绘制注释、将背景和注释合并到已保存的临时文件中以用作下一个背景，等等。典型片段：
bitmap = Bitmap.createBitmap(imageSizeX, imageSizeY, Bitmap.Config.ARGB_8888);
位图 = BitmapFactory.decodeFile(路径, 选项);
bitmap.compress(Bitmap.compressFormat.JPEG, 100, 输出);
一切正常，但在某些情况下，保存的图像会添加类似于本文中描述的噪声： 位图调整大小和旋转：线性噪声
引用帖子的作者已解决通过二次采样来解决问题，但我不想这样做。
我已经尝试过这里建议的解决方案： http://www .curious-creature.org/2010/12/08/bitmap-quality-banding-and-dithering/#more-1218 如果我理解正确的话应该通过设置来实现： getWindow().setFormat(PixelFormat.TRANSLUCENT); 强制32位。
这并没有太大变化。设置或不设置抖动标志似乎也没有太大变化。还有其他想法吗？
My Android application loads images, does some processing and saves the processed images on the SD card. I save temporary files to the SD card instead of using buffers. For example, reading a background, scrolling the image, drawing an annotation, merging background and annotation in a saved temp file to use as next background, and so forth. Typical snippets:
bitmap = Bitmap.createBitmap(imageSizeX, imageSizeY, Bitmap.Config.ARGB_8888);
bitmap = BitmapFactory.decodeFile(path, options);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, output);
Everything works fine but in some cases the saved images have added noise similar to that described in this post:
Bitmap resizing and rotating: linear noise
The author of the post cited solved the problem by subsampling, but I don't wish to do that.
I have tried the solutions suggested here:
http://www.curious-creature.org/2010/12/08/bitmap-quality-banding-and-dithering/#more-1218
which if I understand correctly should be achieved by setting:
getWindow().setFormat(PixelFormat.TRANSLUCENT);
to force 32 bit.
which does not change much. Setting or not setting the dither flag does not seem to change much either. Any other ideas?
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回答我自己的问题：
通过压缩为 .png 而不是 .jpg，噪音消失了，或者至少结果更好了。
在 .jpg 中看起来像地毯纹理的天空在 .png 中看起来光滑干净。由于差异比压缩为 .png 和 .jpg 的同一图像之间的通常差异要明显得多，我想这取决于 Android 的实现。显式设置 TRANSLUCENT 和 DITHER 并不会以某种方式产生太大差异。
In answer to my own question:
The noise disappears, or at least the result is way better, by compressing to .png instead of .jpg
The same sky which looks like a carpet texture in .jpg looks smooth and clean in .png. Since the difference is much more evident than the usual difference between the same image compressed to .png and .jpg, I guess it depends on the Android implementation. Setting explicitly TRANSLUCENT and DITHER does not make much difference one way or another.