/*******************************************************************************
 * Copyright (c) 2000, 2007 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.jface.resource.CompositeImageDescriptor;

import dwtx.jface.resource.ImageDescriptor;

import dwt.graphics.ImageData;
import dwt.graphics.PaletteData;
import dwt.graphics.Point;
import dwt.graphics.RGB;

import dwt.dwthelper.utils;

/**
 * Abstract base class for image descriptors that synthesize an image from other
 * images in order to simulate the effect of custom drawing. For example, this
 * could be used to superimpose a red bar dexter symbol across an image to
 * indicate that something was disallowed.
 * <p>
 * Subclasses must implement the <code>getSize</code> and <code>fill</code>
 * methods. Little or no work happens until the image descriptor's image is
 * actually requested by a call to <code>createImage</code> (or to
 * <code>getImageData</code> directly).
 * </p>
 */
public abstract class CompositeImageDescriptor : ImageDescriptor {

    /**
     * The image data for this composite image.
     */
    private ImageData imageData;

    /**
     * Constructs an uninitialized composite image.
     */
    protected this() {
    }

    /**
     * Draw the composite images.
     * <p>
     * Subclasses must implement this framework method to paint images within
     * the given bounds using one or more calls to the <code>drawImage</code>
     * framework method.
     * </p>
     *
     * @param width
     *            the width
     * @param height
     *            the height
     */
    protected abstract void drawCompositeImage(int width, int height);

    /**
     * Draws the given source image data into this composite image at the given
     * position.
     * <p>
     * Call this internal framework method to superimpose another image atop
     * this composite image.
     * </p>
     *
     * @param src
     *            the source image data
     * @param ox
     *            the x position
     * @param oy
     *            the y position
     */
    final protected void drawImage(ImageData src, int ox, int oy) {
        ImageData dst = imageData;
        PaletteData srcPalette = src.palette;
        ImageData srcMask = null;
        int alphaMask = 0, alphaShift = 0;
        if (src.maskData !is null) {
            srcMask = src.getTransparencyMask ();
            if (src.depth is 32) {
                alphaMask = ~(srcPalette.redMask | srcPalette.greenMask | srcPalette.blueMask);
                while (alphaMask !is 0 && ((alphaMask >>> alphaShift) & 1) is 0) alphaShift++;
            }
        }
        for (int srcY = 0, dstY = srcY + oy; srcY < src.height; srcY++, dstY++) {
            for (int srcX = 0, dstX = srcX + ox; srcX < src.width; srcX++, dstX++) {
                if (!(0 <= dstX && dstX < dst.width && 0 <= dstY && dstY < dst.height)) continue;
                int srcPixel = src.getPixel(srcX, srcY);
                int srcAlpha = 255;
                if (src.maskData !is null) {
                    if (src.depth is 32) {
                        srcAlpha = (srcPixel & alphaMask) >>> alphaShift;
                        if (srcAlpha is 0) {
                            srcAlpha = srcMask.getPixel(srcX, srcY) !is 0 ? 255 : 0;
                        }
                    } else {
                        if (srcMask.getPixel(srcX, srcY) is 0) srcAlpha = 0;
                    }
                } else if (src.transparentPixel !is -1) {
                    if (src.transparentPixel is srcPixel) srcAlpha = 0;
                } else if (src.alpha !is -1) {
                    srcAlpha = src.alpha;
                } else if (src.alphaData !is null) {
                    srcAlpha = src.getAlpha(srcX, srcY);
                }
                if (srcAlpha is 0) continue;
                int srcRed, srcGreen, srcBlue;
                if (srcPalette.isDirect) {
                    srcRed = srcPixel & srcPalette.redMask;
                    srcRed = (srcPalette.redShift < 0) ? srcRed >>> -srcPalette.redShift : srcRed << srcPalette.redShift;
                    srcGreen = srcPixel & srcPalette.greenMask;
                    srcGreen = (srcPalette.greenShift < 0) ? srcGreen >>> -srcPalette.greenShift : srcGreen << srcPalette.greenShift;
                    srcBlue = srcPixel & srcPalette.blueMask;
                    srcBlue = (srcPalette.blueShift < 0) ? srcBlue >>> -srcPalette.blueShift : srcBlue << srcPalette.blueShift;
                } else {
                    RGB rgb = srcPalette.getRGB(srcPixel);
                    srcRed = rgb.red;
                    srcGreen = rgb.green;
                    srcBlue = rgb.blue;
                }
                int dstRed, dstGreen, dstBlue, dstAlpha;
                if (srcAlpha is 255) {
                    dstRed = srcRed;
                    dstGreen = srcGreen;
                    dstBlue= srcBlue;
                    dstAlpha = srcAlpha;
                } else {
                    int dstPixel = dst.getPixel(dstX, dstY);
                    dstAlpha = dst.getAlpha(dstX, dstY);
                    dstRed = (dstPixel & 0xFF) >>> 0;
                    dstGreen = (dstPixel & 0xFF00) >>> 8;
                    dstBlue = (dstPixel & 0xFF0000) >>> 16;
                    dstRed += (srcRed - dstRed) * srcAlpha / 255;
                    dstGreen += (srcGreen - dstGreen) * srcAlpha / 255;
                    dstBlue += (srcBlue - dstBlue) * srcAlpha / 255;
                    dstAlpha += (srcAlpha - dstAlpha) * srcAlpha / 255;
                }
                dst.setPixel(dstX, dstY, ((dstRed & 0xFF) << 0) | ((dstGreen & 0xFF) << 8) | ((dstBlue & 0xFF) << 16));
                dst.setAlpha(dstX, dstY, dstAlpha);
            }
        }
    }

    /*
     * (non-Javadoc) Method declared on ImageDesciptor.
     */
    public override ImageData getImageData() {
        Point size = getSize();

        /* Create a 24 bit image data with alpha channel */
        imageData = new ImageData(size.x, size.y, 24, new PaletteData(0xFF, 0xFF00, 0xFF0000));
        imageData.alphaData = new byte[imageData.width * imageData.height];

        drawCompositeImage(size.x, size.y);

        /* Detect minimum transparency */
        bool transparency = false;
        byte[] alphaData = imageData.alphaData;
        for (int i = 0; i < alphaData.length; i++) {
            int alpha = alphaData[i] & 0xFF;
            if (!(alpha is 0 || alpha is 255)) {
                /* Full alpha channel transparency */
                return imageData;
            }
            if (!transparency && alpha is 0) transparency = true;
        }
        if (transparency) {
            /* Reduce to 1-bit alpha channel transparency */
            PaletteData palette = new PaletteData([new RGB(0, 0, 0), new RGB(255, 255, 255)]);
            ImageData mask = new ImageData(imageData.width, imageData.height, 1, palette);
            for (int y = 0; y < mask.height; y++) {
                for (int x = 0; x < mask.width; x++) {
                    mask.setPixel(x, y, imageData.getAlpha(x, y) is 255 ? 1 : 0);
                }
            }
        } else {
            /* no transparency */
            imageData.alphaData = null;
        }
        return imageData;
    }


    /**
     * Return the transparent pixel for the receiver.
     * <strong>NOTE</strong> This value is not currently in use in the
     * default implementation.
     * @return int
     * @since 3.3
     */
    protected int getTransparentPixel() {
        return 0;
    }

    /**
     * Return the size of this composite image.
     * <p>
     * Subclasses must implement this framework method.
     * </p>
     *
     * @return the x and y size of the image expressed as a point object
     */
    protected abstract Point getSize();

    /**
     * @param imageData The imageData to set.
     * @since 3.3
     */
    protected void setImageData(ImageData imageData) {
        this.imageData = imageData;
    }
}