public Bitmap
inBitmap
If set, decode methods that take the Options objectwill attempt to reuse this bitmap when loading content.
public int
inDensity
The pixel density to use for the bitmap.
public boolean
inDither
If dither is true, the decoder will attempt todither the decoded image.
public boolean
inInputShareable
This field works in conjuction withinPurgeable.
public boolean
inJustDecodeBounds
If set to true, the decoder will return null (nobitmap), but the out…
public boolean
inMutable
If set, decode methods will always return a mutableBitmap instead of an immutable one.
public boolean
inPreferQualityOverSpeed
If inPreferQualityOverSpeed is set to true, thedecoder will try to decode the reconstructed image to a higherquality even at the expense of the decoding speed.
publicBitmap.Config
inPreferredConfig
If this is non-null, the decoder will try to decodeinto this internal configuration.
public boolean
inPurgeable
If this is set to true, then the resulting bitmapwill allocate its pixels such that they can be purged if the systemneeds to reclaim memory.
public int
inSampleSize
If set to a value > 1, requests the decoder tosubsample the original image, returning a smaller image to savememory.
public boolean
inScaled
When this flag is set,if inDensity and inTargetDensity arenot 0, the bitmap will be scaled tomatch inTargetDensity whenloaded, rather than relying on the graphics system scaling it eachtime it is drawn to a Canvas.
public int
inScreenDensity
The pixel density of the actual screen that isbeing used.
public int
inTargetDensity
The pixel density of the destination this bitmapwill be drawn to.
public byte[]
inTempStorage
Temp storage to use for decoding.
public boolean
mCancel
Flag to indicate that cancel has been called onthis object.
public int
outHeight
The resulting height of the bitmap, set independentof the state of inJustDecodeBounds.
public String
outMimeType
If known, this string is set to the mimetype of thedecoded image.
public int
outWidth
The resulting width of the bitmap, set independentof the state of inJustDecodeBounds.
这个表格是从android sdk文档里摘出来的，简单看一下说明就明白是什么意思了。
下面我们回到我们的主题上来：怎样获取图片的大小？
思路很简单：
首先我们把这个图片转成Bitmap，然后再利用Bitmap的getWidth()和getHeight()方法就可以取到图片的宽高了。
新问题又来了，在通过BitmapFactory.decodeFile(Stringpath)方法将突破转成Bitmap时，遇到大一些的图片，我们经常会遇到OOM(Out OfMemory)的问题。怎么避免它呢？
这就用到了我们上面提到的BitmapFactory.Options这个类。
BitmapFactory.Options这个类，有一个字段叫做 inJustDecodeBounds 。SDK中对这个成员的说明是这样的：
If set to true, the decoderwill return null (no bitmap), but theout…
也就是说，如果我们把它设为true，那么BitmapFactory.decodeFile(Stringpath, Optionsopt)并不会真的返回一个Bitmap给你，它仅仅会把它的宽，高取回来给你，这样就不会占用太多的内存，也就不会那么频繁的发生OOM了。
示例代码如下：
BitmapFactory.Options options = newBitmapFactory.Options();
options.inJustDecodeBounds = true;
Bitmap bmp = BitmapFactory.decodeFile(path, options);
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这段代码之后，options.outWidth 和 options.outHeight就是我们想要的宽和高了。
有了宽，高的信息，我们怎样在图片不变形的情况下获取到图片指定大小的缩略图呢？
比如我们需要在图片不变形的前提下得到宽度为200的缩略图。
那么我们需要先计算一下缩放之后，图片的高度是多少
int height = options.outHeight * 200 / options.outWidth;
options.outWidth = 200；
options.outHeight = height;
options.inJustDecodeBounds = false;
Bitmap bmp = BitmapFactory.decodeFile(path, options);
image.setImageBitmap(bmp);
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这样虽然我们可以得到我们期望大小的ImageView
但是在执行BitmapFactory.decodeFile(path,options);时，并没有节约内存。要想节约内存，还需要用到BitmapFactory.Options这个类里的 inSampleSize 这个成员变量。
我们可以根据图片实际的宽高和我们期望的宽高来计算得到这个值。
inSampleSize = options.outWidth / 200;
另外，为了节约内存我们还可以使用下面的几个字段：
options.inPreferredConfig =Bitmap.Config.ARGB_4444; //默认是Bitmap.Config.ARGB_8888
options.inPurgeable = true;
options.inInputShareable = true;
加载和显示图片是很消耗内存的一件事，BitmapFactory.Options 类, 允许我们定义图片以何种方式如何读到内存，
[html]
BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
bmpFactoryOptions.inSampleSize = 8;
Bitmap bmp = BitmapFactory.decodeFile(imageFilePath, bmpFactoryOptions);
imv.setImageBitmap(bmp);
上面的代码使图片变成原来的1/8.
[html]
//imv = (ImageView) findViewById(R.id.ReturnedImageView);
Display currentDisplay = getWindowManager().getDefaultDisplay();
int dw = currentDisplay.getWidth();
int dh = currentDisplay.getHeight();
try
{
BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
bmpFactoryOptions.inJustDecodeBounds = true;
Bitmap bmp = BitmapFactory.decodeStream(getContentResolver().
openInputStream(imageFileUri), null, bmpFactoryOptions);
int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)dh);
int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)dw);
