［Android］BitmapのConfigフォーマットの設定とConfigパラメータのソースを修正して読みます.
オリジナルブログ、転載は出所を明記してください:http://blog.csdn.net/u011035622/article/details/50277565
Bitmap.C.onfigの紹介
まずConfig設定のパラメータを紹介しましょう.読者に分かりやすくする一方で、自分にも印象を与えます.Bitmap.C.onfigは全部で4つのパラメータがあります.
/**
* Possible bitmap configurations. A bitmap configuration describes
* how pixels are stored. This affects the quality (color depth) as
* well as the ability to display transparent/translucent colors.
*/
public enum Config {
// these native values must match up with the enum in SkBitmap.h
/**
* 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.
*/
ALPHA_8 (1),
/**
* 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.
*/
RGB_565 (3),
/**
* 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 {@link #ARGB_8888} instead of this
* configuration.
*
* Note: as of {@link android.os.Build.VERSION_CODES#KITKAT},
* any bitmap created with this configuration will be created
* using {@link #ARGB_8888} instead.
*
* @deprecated Because of the poor quality of this configuration,
* it is advised to use {@link #ARGB_8888} instead.
*/
@Deprecated
ARGB_4444 (4),
/**
* 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.
*/
ARGB_8888 (5);
final int nativeInt;
@SuppressWarnings({"deprecation"})
private static Config sConfigs[] = {
null, ALPHA_8, null, RGB_565, ARGB_4444, ARGB_8888
};
Config(int ni) {
this.nativeInt = ni;
}
static Config nativeToConfig(int ni) {
return sConfigs[ni];
}
} ， 。
修正時に発生した問題
もしローカル画像のパスであれば、直接にこのような方法でbitmapを得てOptions.inPreferredConfigを通じて彼のCofigパラメータを設定することができます.
Bitmap bitmap = null;
File file = new File(path);
if(file.exists()) {
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
try {
bitmap = BitmapFactory.decodeFile(path, opts);
} catch (OutOfMemoryError error) {
bitmap = null;
}
}bitmap.setConfig(Bitmap.Config.ARGB_8888);問題の解決方法
よく振り回されていますが、どこが間違っているか分かりません.ソースコードを見てから分かります.
set Config、reconfigur方法は、現在使用されているビットマップには使用できません!!!=.(最後に公式ソースを貼った読者は参考にしてみてもいいです.)
考えてみると、現在のビットストリームを先にビットストリームに変換し、ビットストリームをBitmapfactoryで設定に従って再生成するしかない.やはり、問題解決:
/* bitmap ， bitmap。*/
ByteArrayOutputStream dataByte = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 100, dataByte);
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = OPT_INSAMPLE_SIZE;
opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
bitmap = BitmapFactory.decodeByteArray(dataByte.toByteArray(), 0, dataByte.size(), opts);最後にsetConfigの公式ソース部分を貼り付けます.
/**
* Convenience method for calling {@link #reconfigure(int, int, Config)} with the current height and width.
*( bitmap＝。＝)
* WARNING: this method should not be used on bitmaps currently used by the view system, see {@link #reconfigure(int, int, Config)} for more details. */
public void setConfig(Config config) {
reconfigure(getWidth(), getHeight(), config);
}また、Bitmapの修正はhasalphaに影響を与える可能性があります.つまり、フォーマットの変更は透明な通路があるかないかということです.2、ビットマップの配置があまり大きくない場合、新しい構成をサポートします.ILL Argement Exceptionは抛り出します.ビットマップは修正されません.
/**
* Modifies the bitmap to have a specified width, height, and {@link
* Config}, without affecting the underlying allocation backing the bitmap.
* Bitmap pixel data is not re-initialized for the new configuration.
*
* This method can be used to avoid allocating a new bitmap, instead
* reusing an existing bitmap's allocation for a new configuration of equal
* or lesser size. If the Bitmap's allocation isn't large enough to support
* the new configuration, an IllegalArgumentException will be thrown and the
* bitmap will not be modified.
*
* The result of {@link #getByteCount()} will reflect the new configuration,
* while {@link #getAllocationByteCount()} will reflect that of the initial
* configuration.
*
* Note: This may change this result of hasAlpha(). When converting to 565,
* the new bitmap will always be considered opaque. When converting from 565,
* the new bitmap will be considered non-opaque, and will respect the value
* set by setPremultiplied().
*
* WARNING: This method should NOT be called on a bitmap currently used
* by the view system. It does not make guarantees about how the underlying
* pixel buffer is remapped to the new config, just that the allocation is
* reused. Additionally, the view system does not account for bitmap
* properties being modifying during use, e.g. while attached to
* drawables.
*
* @see #setWidth(int)
* @see #setHeight(int)
* @see #setConfig(Config)
*/
public void reconfigure(int width, int height, Config config) {
checkRecycled("Can't call reconfigure() on a recycled bitmap");
if (width <= 0 || height <= 0) {
throw new IllegalArgumentException("width and height must be > 0");
}
if (!isMutable()) {
throw new IllegalStateException("only mutable bitmaps may be reconfigured");
}
if (mBuffer == null) {
throw new IllegalStateException("native-backed bitmaps may not be reconfigured");
}
nativeReconfigure(mNativeBitmap, width, height, config.nativeInt, mBuffer.length,
mRequestPremultiplied);
mWidth = width;
mHeight = height;
}