An implementation based upon {@link BufferedImage}. This provides access to the * underlying image as if it were a monochrome image. Behind the scenes, it is evaluating * the luminance of the underlying image by retrieving its pixels' RGB values.
- * - * @author srowen@google.com (Sean Owen) + * + *This may also be used to construct a {@link MonochromeBitmapSource} + * based on a region of a {@link BufferedImage}; see + * {@link #BufferedImageMonochromeBitmapSource(BufferedImage, int, int, int, int)}.
+ * + * @author srowen@google.com (Sean Owen), Daniel Switkin (dswitkin@google.com) */ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitmapSource { private final BufferedImage image; - private final int blackPoint; + private final int left; + private final int top; + private final int width; + private final int height; + private int blackPoint; + private BlackPointEstimationMethod lastMethod; + private int lastArgument; + private static final int LUMINANCE_BITS = 5; + private static final int LUMINANCE_SHIFT = 8 - LUMINANCE_BITS; + private static final int LUMINANCE_BUCKETS = 1 << LUMINANCE_BITS; + + /** + * Creates an instance that uses the entire given image as a source of pixels to decode. + * + * @param image image to decode + */ public BufferedImageMonochromeBitmapSource(BufferedImage image) { + this(image, 0, 0, image.getWidth(), image.getHeight()); + } + + /** + * Creates an instance that uses only a region of the given image as a source of pixels to decode. + * + * @param image image to decode a region of + * @param left x coordinate of leftmost pixels to decode + * @param top y coordinate of topmost pixels to decode + * @param right one more than the x coordinate of rightmost pixels to decode. That is, we will decode + * pixels whose x coordinate is in [left,right) + * @param bottom likewise, one more than the y coordinate of the bottommost pixels to decode + */ + public BufferedImageMonochromeBitmapSource(BufferedImage image, int left, int top, int right, int bottom) { this.image = image; - int width = image.getWidth(); - int height = image.getHeight(); - int[] luminanceBuckets = new int[32]; - int minDimension = width < height ? width : height; - int startI = height == minDimension ? 0 : (height - width) >> 1; - int startJ = width == minDimension ? 0 : (width - height) >> 1; - for (int n = 0; n < minDimension; n++) { - int pixel = image.getRGB(startJ + n, startI + n); - luminanceBuckets[computeRGBLuminance(pixel) >> 3]++; + blackPoint = 0x7F; + lastMethod = null; + lastArgument = 0; + int sourceHeight = image.getHeight(); + int sourceWidth = image.getWidth(); + if (left < 0 || top < 0 || right > sourceWidth || bottom > sourceHeight || right <= left || bottom <= top) { + throw new IllegalArgumentException("Invalid bounds: (" + top + ',' + left + ") (" + right + ',' + bottom + ')'); } - blackPoint = BlackPointEstimator.estimate(luminanceBuckets) << 3; + this.left = left; + this.top = top; + this.width = right - left; + this.height = bottom - top; + } + + /** + * @return underlying {@link BufferedImage} behind this instance. Note that even if this instance + * only uses a subset of the full image, the returned value here represents the entire backing image. + */ + public BufferedImage getImage() { + return image; + } + + private int getRGB(int x, int y) { + return image.getRGB(left + x, top + y); + } + + private void getRGBRow(int startX, int startY, int[] result) { + image.getRGB(left + startX, top + startY, result.length, 1, result, 0, result.length); } public boolean isBlack(int x, int y) { - return computeRGBLuminance(image.getRGB(x, y)) < blackPoint; + return computeRGBLuminance(getRGB(x, y)) < blackPoint; } public BitArray getBlackRow(int y, BitArray row, int startX, int getWidth) { @@ -59,7 +114,8 @@ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitm } else { row.clear(); } - int[] pixelRow = image.getRGB(startX, y, getWidth, 1, null, 0, getWidth); + int[] pixelRow = new int[getWidth]; + getRGBRow(startX, y, pixelRow); for (int i = 0; i < getWidth; i++) { if (computeRGBLuminance(pixelRow[i]) < blackPoint) { row.set(i); @@ -69,11 +125,68 @@ public final class BufferedImageMonochromeBitmapSource implements MonochromeBitm } public int getHeight() { - return image.getHeight(); + return height; } public int getWidth() { - return image.getWidth(); + return width; + } + + public void estimateBlackPoint(BlackPointEstimationMethod method, int argument) throws ReaderException { + if (!method.equals(lastMethod) || argument != lastArgument) { + int[] histogram = new int[LUMINANCE_BUCKETS]; + if (method.equals(BlackPointEstimationMethod.TWO_D_SAMPLING)) { + int minDimension = width < height ? width : height; + int startI = height == minDimension ? 0 : (height - width) >> 1; + int startJ = width == minDimension ? 0 : (width - height) >> 1; + for (int n = 0; n < minDimension; n++) { + int pixel = getRGB(startJ + n, startI + n); + histogram[computeRGBLuminance(pixel) >> LUMINANCE_SHIFT]++; + } + } else if (method.equals(BlackPointEstimationMethod.ROW_SAMPLING)) { + if (argument < 0 || argument >= height) { + throw new IllegalArgumentException("Row is not within the image: " + argument); + } + int[] rgbArray = new int[width]; + getRGBRow(0, argument, rgbArray); + for (int x = 0; x < width; x++) { + histogram[computeRGBLuminance(rgbArray[x]) >> LUMINANCE_SHIFT]++; + } + } else { + throw new IllegalArgumentException("Unknown method: " + method); + } + blackPoint = BlackPointEstimator.estimate(histogram) << LUMINANCE_SHIFT; + lastMethod = method; + lastArgument = argument; + } + } + + public BlackPointEstimationMethod getLastEstimationMethod() { + return lastMethod; + } + + public MonochromeBitmapSource rotateCounterClockwise() { + if (!isRotateSupported()) { + throw new IllegalStateException("Rotate not supported"); + } + int sourceWidth = image.getWidth(); + int sourceHeight = image.getHeight(); + // 90 degrees counterclockwise: + AffineTransform transform = new AffineTransform(0.0, -1.0, 1.0, 0.0, 0.0, sourceWidth); + BufferedImageOp op = new AffineTransformOp(transform, AffineTransformOp.TYPE_NEAREST_NEIGHBOR); + // Note width/height are flipped since we are rotating 90 degrees: + BufferedImage rotatedImage = new BufferedImage(sourceHeight, sourceWidth, image.getType()); + op.filter(image, rotatedImage); + return new BufferedImageMonochromeBitmapSource(rotatedImage, + top, + sourceWidth - (left + width), + top + height, + sourceWidth - left); + } + + public boolean isRotateSupported() { + // Can't run AffineTransforms on images of unknown format + return image.getType() != BufferedImage.TYPE_CUSTOM; } /**