RelativeCroppingString.java

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package io.wcm.handler.mediasource.dam.impl.weboptimized;

import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.NumberFormat;
import java.util.Locale;

import org.jetbrains.annotations.NotNull;

import io.wcm.handler.media.CropDimension;
import io.wcm.handler.media.Dimension;

/**
 * Creates relative crop string with percentage values as required by the Web-Optimized Image Delivery API.
 * It uses one fractional digit for the percentage values.
 */
final class RelativeCroppingString {

  private static final NumberFormat DECIMAL_FORMAT = new DecimalFormat("0.0", new DecimalFormatSymbols(Locale.US));

  private RelativeCroppingString() {
    // static methods only
  }

  static @NotNull String createFromCropDimension(
      @NotNull CropDimension cropDimension, @NotNull Dimension imageDimension) {
    double x1 = cropDimension.getLeft();
    double y1 = cropDimension.getTop();
    double left = x1 / imageDimension.getWidth();
    double top = y1 / imageDimension.getHeight();
    double width = (double)cropDimension.getWidth() / imageDimension.getWidth();
    double height = (double)cropDimension.getHeight() / imageDimension.getHeight();
    return create(left, top, width, height);
  }

  static @NotNull String create(double left, double top, double width, double height) {
    return String.format("%sp,%sp,%sp,%sp",
        toPercentage(left), toPercentage(top),
        toPercentage(width), toPercentage(height));
  }

  private static String toPercentage(double fraction) {
    double percentage = Math.round(fraction * 1000d) / 10d;
    percentage = Math.max(0.0, percentage);
    percentage = Math.min(100.0, percentage);
    return DECIMAL_FORMAT.format(percentage);
  }

}