com.bumptech.glide.load.resource.bitmap.DownsampleStrategy Maven / Gradle / Ivy
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package com.bumptech.glide.load.resource.bitmap;
import com.bumptech.glide.util.Synthetic;
/**
* Indicates the algorithm to use when downsampling images.
*/
public abstract class DownsampleStrategy {
/**
* Scales, maintaining the original aspect ratio, so that one of the image's dimensions is
* exactly equal to the requested size and the other dimension is less than or equal to the
* requested size.
*
* This method will upscale if the requested width and height are greater than the source width
* and height. To avoid upscaling, use {@link #AT_LEAST}, {@link #AT_MOST} or
* {@link #CENTER_INSIDE}.
*
*
On pre-KitKat devices, this is equivalent to {@link #AT_MOST} because only power of
* two downsampling can be used.
*/
public static final DownsampleStrategy FIT_CENTER = new FitCenter();
/**
* Scales, maintaining the original aspect ratio, so that one of the image's dimensions is
* exactly equal to the requested size and the other dimension is greater than or equal to
* the requested size.
*
*
This method will upscale if the requested width and height are greater than the source width
* and height. To avoid upscaling, use {@link #AT_LEAST}, {@link #AT_MOST},
* or {@link #CENTER_INSIDE}.
*
*
On pre-KitKat devices, this is equivalent to {@link #AT_LEAST} because only power of
* two downsampling can be used.
*/
public static final DownsampleStrategy CENTER_OUTSIDE = new CenterOutside();
/**
* Downsamples so the image's smallest dimension is between the given dimensions and 2x the given
* dimensions, with no size restrictions on the image's largest dimension.
*/
public static final DownsampleStrategy AT_LEAST = new AtLeast();
/**
* Downsamples so the image's largest dimension is between 1/2 the given dimensions and the given
* dimensions, with no restrictions on the image's smallest dimension.
*/
public static final DownsampleStrategy AT_MOST = new AtMost();
/**
* Returns the original image if it is smaller than the target, otherwise it will be downscaled
* maintaining its original aspect ratio, so that one of the image's dimensions is exactly equal
* to the requested size and the other is less or equal than the requested size.
*
*
This method will not upscale.
*/
public static final DownsampleStrategy CENTER_INSIDE = new CenterInside();
/**
* Performs no downsampling or scaling.
*/
public static final DownsampleStrategy NONE = new None();
/**
* Default strategy, currently {@link #CENTER_OUTSIDE}.
*/
public static final DownsampleStrategy DEFAULT = CENTER_OUTSIDE;
/**
* Returns a float (0, +infinity) indicating a scale factor to apply to the source
* width and height when displayed in the requested width and height.
*
* The returned scale factor will be split into a power of two sample size applied via
* {@link android.graphics.BitmapFactory.Options#inSampleSize} and a float scale factor applied
* after downsampling via {@link android.graphics.BitmapFactory.Options#inTargetDensity} and
* {@link android.graphics.BitmapFactory.Options#inDensity}. Because of rounding errors the scale
* factor may not be applied precisely.
*
*
The float scaling factor will only be applied on KitKat+. Prior to KitKat, only the power
* of two downsampling will be applied.
*
* @param sourceWidth The width in pixels of the image to be downsampled.
* @param sourceHeight The height in pixels of the image to be downsampled.
* @param requestedWidth The width in pixels of the view/target the image will be displayed in.
* @param requestedHeight The height in pixels of the view/target the image will be displayed in.
*/
public abstract float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight);
/**
* Returns a non-null {@link SampleSizeRounding} to use to resolve rounding errors and conflicts
* between scaling for the width and the height of the image.
*
* @param sourceWidth The width in pixels of the image to be downsampled.
* @param sourceHeight The height in pixels of the image to be downsampled.
* @param requestedWidth The width in pixels of the view/target the image will be displayed in.
* @param requestedHeight The height in pixels of the view/target the image will be displayed in.
*/
public abstract SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight);
private static class FitCenter extends DownsampleStrategy {
@Synthetic
FitCenter() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
float widthPercentage = requestedWidth / (float) sourceWidth;
float heightPercentage = requestedHeight / (float) sourceHeight;
return Math.min(widthPercentage, heightPercentage);
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.QUALITY;
}
}
private static class CenterOutside extends DownsampleStrategy {
@Synthetic
CenterOutside() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
float widthPercentage = requestedWidth / (float) sourceWidth;
float heightPercentage = requestedHeight / (float) sourceHeight;
return Math.max(widthPercentage, heightPercentage);
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.QUALITY;
}
}
private static class AtLeast extends DownsampleStrategy {
@Synthetic
AtLeast() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
int minIntegerFactor = Math.min(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
return minIntegerFactor == 0 ? 1f : 1f / Integer.highestOneBit(minIntegerFactor);
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.QUALITY;
}
}
private static class AtMost extends DownsampleStrategy {
@Synthetic
AtMost() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
int maxIntegerFactor = (int) Math.ceil(Math.max(sourceHeight / (float) requestedHeight,
sourceWidth / (float) requestedWidth));
int lesserOrEqualSampleSize = Math.max(1, Integer.highestOneBit(maxIntegerFactor));
int greaterOrEqualSampleSize =
lesserOrEqualSampleSize << (lesserOrEqualSampleSize < maxIntegerFactor ? 1 : 0);
return 1f / greaterOrEqualSampleSize;
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.MEMORY;
}
}
private static class None extends DownsampleStrategy {
@Synthetic
None() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
return 1f;
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.QUALITY;
}
}
private static class CenterInside extends DownsampleStrategy {
@Synthetic
CenterInside() { }
@Override
public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
int requestedHeight) {
return Math.min(1.f,
FIT_CENTER.getScaleFactor(sourceWidth, sourceHeight, requestedWidth, requestedHeight));
}
@Override
public SampleSizeRounding getSampleSizeRounding(int sourceWidth, int sourceHeight,
int requestedWidth, int requestedHeight) {
return SampleSizeRounding.QUALITY;
}
}
/**
* Indicates whether to prefer to prefer downsampling or scaling to prefer lower memory usage
* or higher quality.
*/
public enum SampleSizeRounding {
/**
* Prefer to round the sample size up so that the image is downsampled to smaller than the
* requested size to use less memory.
*/
MEMORY,
/**
* Prefer to round the sample size down so that the image is downsampled to larger than the
* requested size to maintain quality at the expense of extra memory usage.
*/
QUALITY,
}
}