标签：内存优化 bitmap 图片优化 计算内存 像素字节数
在Android开发中，我现在发现很多人还不会对图片占用内存进行很好的计算。
因此撰写该博文来做介绍，期望达到抛砖引玉的作用。
| Enum Values | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
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Bitmap.Config |
ALPHA_8 |
Each pixel is stored as a single translucency (alpha) channel. This is very useful to efficiently store masks for instance. No color information is stored. With this configuration, each pixel requires 1 byte of memory. 此时图片只有alpha值，没有RGB值， 一个像素占用一个字节 |
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Bitmap.Config |
ARGB_4444 |
This field is deprecated. Because of the poor quality of this configuration, it is advised to use ARGB_8888instead. 这种格式的图片，看起来质量太差，已经不推荐使用。 Each pixel is stored on 2 bytes. The three RGB color channels and the alpha channel (translucency) are stored with a 4 bits precision (16 possible values.) This configuration is mostly useful if the application needs to store translucency information but also needs to save memory. It is recommended to use ARGB_8888 instead of this configuration. 一个像素占用2个字节，alpha(A)值，Red（R）值，Green(G)值，Blue（B）值各占4个bites 共16bites,即2个字节 |
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|
Bitmap.Config |
ARGB_8888 |
Each pixel is stored on 4 bytes. Each channel (RGB and alpha for translucency) is stored with 8 bits of precision (256 possible values.) This configuration is very flexible and offers the best quality. It should be used whenever possible 一个像素占用4个字节，alpha(A)值，Red（R）值，Green(G)值，Blue（B）值各占8个bites 共32bites,即4个字节 这是一种高质量的图片格式，电脑上普通采用的格式。它也是Android手机上一个BitMap的默认格式。 |
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|
Bitmap.Config |
RGB_565 |
Each pixel is stored on 2 bytes and only the RGB channels are encoded: red is stored with 5 bits of precision (32 possible values), green is stored with 6 bits of precision (64 possible values) and blue is stored with 5 bits of precision. This configuration can produce slight visual artifacts depending on the configuration of the source. For instance, without dithering, the result might show a greenish tint. To get better results dithering should be applied. This configuration may be useful when using opaque bitmaps that do not require high color fidelity. 一个像素占用2个字节，没有alpha(A)值，即不支持透明和半透明， Red（R）值占5个bites 对于没有透明和半透明颜色的图片来说，该格式的图片能够达到比较的呈现效果， 相对于ARGB_8888来说也能减少一半的内存开销。因此它是一个不错的选择。 另外我们通过android.content.res.Resources来取得一个张图片时，它也是以该格式来构建BitMap的 从Android4.0开始，该选项无效。即使设置为该值，系统任然会采用 |
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Android 一张图片（BitMap）占用内存的计算 图片内存优化
标签：内存优化 bitmap 图片优化 计算内存 像素字节数
原文地址：http://blog.csdn.net/caoyouxing/article/details/39547893
