BitmapFactory.Options

If set, decode methods that take the Options object will attempt to reuse this bitmap when loading content. If the decode operation cannot use this bitmap, the decode method will return null and will throw an IllegalArgumentException. The current implementation necessitates that the reused bitmap be mutable, and the resulting reused bitmap will continue to remain mutable even when decoding a resource which would normally result in an immutable bitmap.

You should still always use the returned Bitmap of the decode method and not assume that reusing the bitmap worked, due to the constraints outlined above and failure situations that can occur. Checking whether the return value matches the value of the inBitmap set in the Options structure will indicate if the bitmap was reused, but in all cases you should use the Bitmap returned by the decoding function to ensure that you are using the bitmap that was used as the decode destination.

Usage with BitmapFactory

As of KITKAT, any mutable bitmap can be reused by BitmapFactory to decode any other bitmaps as long as the resulting byte count of the decoded bitmap is less than or equal to the allocated byte count of the reused bitmap. This can be because the intrinsic size is smaller, or its size post scaling (for density / sample size) is smaller.

Prior to KITKAT additional constraints apply: The image being decoded (whether as a resource or as a stream) must be in jpeg or png format. Only equal sized bitmaps are supported, with inSampleSize set to 1. Additionally, the configuration of the reused bitmap will override the setting of inPreferredConfig, if set.

Usage with BitmapRegionDecoder

BitmapRegionDecoder will draw its requested content into the Bitmap provided, clipping if the output content size (post scaling) is larger than the provided Bitmap. The provided Bitmap's width, height, and Bitmap.Config will not be changed.

BitmapRegionDecoder support for inBitmap was introduced in JELLY_BEAN. All formats supported by BitmapRegionDecoder support Bitmap reuse via inBitmap.

The pixel density to use for the bitmap. This will always result in the returned bitmap having a density set for it (see Bitmap.setDensity(int)). In addition, if inScaled is set (which it is by default} and this density does not match inTargetDensity, then the bitmap will be scaled to the target density before being returned.

If this is 0, decodeResource(Resources, int), decodeResource(Resources, int, android.graphics.BitmapFactory.Options), and decodeResourceStream(Resources, TypedValue, InputStream, Rect, BitmapFactory.Options) will fill in the density associated with the resource. The other functions will leave it as-is and no density will be applied.

If dither is true, the decoder will attempt to dither the decoded image.

This field works in conjuction with inPurgeable. If inPurgeable is false, then this field is ignored. If inPurgeable is true, then this field determines whether the bitmap can share a reference to the input data (inputstream, array, etc.) or if it must make a deep copy.

If set to true, the decoder will return null (no bitmap), but the out... fields will still be set, allowing the caller to query the bitmap without having to allocate the memory for its pixels.

If set, decode methods will always return a mutable Bitmap instead of an immutable one. This can be used for instance to programmatically apply effects to a Bitmap loaded through BitmapFactory.

If inPreferQualityOverSpeed is set to true, the decoder will try to decode the reconstructed image to a higher quality even at the expense of the decoding speed. Currently the field only affects JPEG decode, in the case of which a more accurate, but slightly slower, IDCT method will be used instead.

If this is non-null, the decoder will try to decode into this internal configuration. If it is null, or the request cannot be met, the decoder will try to pick the best matching config based on the system's screen depth, and characteristics of the original image such as if it has per-pixel alpha (requiring a config that also does). Image are loaded with the ARGB_8888 config by default.

If true (which is the default), the resulting bitmap will have its color channels pre-multipled by the alpha channel.

This should NOT be set to false for images to be directly drawn by the view system or through a Canvas. The view system and Canvas assume all drawn images are pre-multiplied to simplify draw-time blending, and will throw a RuntimeException when un-premultiplied are drawn.

This is likely only useful if you want to manipulate raw encoded image data, e.g. with RenderScript or custom OpenGL.

This does not affect bitmaps without an alpha channel.

If this is set to true, then the resulting bitmap will allocate its pixels such that they can be purged if the system needs to reclaim memory. In that instance, when the pixels need to be accessed again (e.g. the bitmap is drawn, getPixels() is called), they will be automatically re-decoded.

For the re-decode to happen, the bitmap must have access to the encoded data, either by sharing a reference to the input or by making a copy of it. This distinction is controlled by inInputShareable. If this is true, then the bitmap may keep a shallow reference to the input. If this is false, then the bitmap will explicitly make a copy of the input data, and keep that. Even if sharing is allowed, the implementation may still decide to make a deep copy of the input data.

While inPurgeable can help avoid big Dalvik heap allocations (from API level 11 onward), it sacrifices performance predictability since any image that the view system tries to draw may incur a decode delay which can lead to dropped frames. Therefore, most apps should avoid using inPurgeable to allow for a fast and fluid UI. To minimize Dalvik heap allocations use the inBitmap flag instead.

Note: This flag is ignored when used with decodeResource(Resources, int, android.graphics.BitmapFactory.Options) or decodeFile(String, android.graphics.BitmapFactory.Options).

If set to a value > 1, requests the decoder to subsample the original image, returning a smaller image to save memory. The sample size is the number of pixels in either dimension that correspond to a single pixel in the decoded bitmap. For example, inSampleSize == 4 returns an image that is 1/4 the width/height of the original, and 1/16 the number of pixels. Any value <= 1 is treated the same as 1. Note: the decoder uses a final value based on powers of 2, any other value will be rounded down to the nearest power of 2.

When this flag is set, if inDensity and inTargetDensity are not 0, the bitmap will be scaled to match inTargetDensity when loaded, rather than relying on the graphics system scaling it each time it is drawn to a Canvas.

BitmapRegionDecoder ignores this flag, and will not scale output based on density. (though inSampleSize is supported)

This flag is turned on by default and should be turned off if you need a non-scaled version of the bitmap. Nine-patch bitmaps ignore this flag and are always scaled.

The pixel density of the actual screen that is being used. This is purely for applications running in density compatibility code, where inTargetDensity is actually the density the application sees rather than the real screen density.

By setting this, you allow the loading code to avoid scaling a bitmap that is currently in the screen density up/down to the compatibility density. Instead, if inDensity is the same as inScreenDensity, the bitmap will be left as-is. Anything using the resulting bitmap must also used Bitmap.getScaledWidth and Bitmap.getScaledHeight to account for any different between the bitmap's density and the target's density.

This is never set automatically for the caller by BitmapFactory itself. It must be explicitly set, since the caller must deal with the resulting bitmap in a density-aware way.

The pixel density of the destination this bitmap will be drawn to. This is used in conjunction with inDensity and inScaled to determine if and how to scale the bitmap before returning it.

If this is 0, decodeResource(Resources, int), decodeResource(Resources, int, android.graphics.BitmapFactory.Options), and decodeResourceStream(Resources, TypedValue, InputStream, Rect, BitmapFactory.Options) will fill in the density associated the Resources object's DisplayMetrics. The other functions will leave it as-is and no scaling for density will be performed.

Temp storage to use for decoding. Suggest 16K or so.

Flag to indicate that cancel has been called on this object. This is useful if there's an intermediary that wants to first decode the bounds and then decode the image. In that case the intermediary can check, inbetween the bounds decode and the image decode, to see if the operation is canceled.

The resulting height of the bitmap, set independent of the state of inJustDecodeBounds. However, if there is an error trying to decode, outHeight will be set to -1.

If known, this string is set to the mimetype of the decoded image. If not know, or there is an error, it is set to null.

The resulting width of the bitmap, set independent of the state of inJustDecodeBounds. However, if there is an error trying to decode, outWidth will be set to -1.

Create a default Options object, which if left unchanged will give the same result from the decoder as if null were passed.

This can be called from another thread while this options object is inside a decode... call. Calling this will notify the decoder that it should cancel its operation. This is not guaranteed to cancel the decode, but if it does, the decoder... operation will return null, or if inJustDecodeBounds is true, will set outWidth/outHeight to -1