imageutil.java

一个小的非常 好用的电子书阅读器源码-a

import javax.microedition.lcdui.*;


public class ImageUtil
{


    // fixed point constants
    private static final int FP_SHIFT=13;

    private static final int FP_ONE=1 << FP_SHIFT;

    private static final int FP_HALF=1 << (FP_SHIFT - 1);

    // resampling modes - valid values for the mode parameter of resizeImage()
    // any other value will default to MODE_BOX_FILTER because of the way the
    // conditionals are set in resizeImage()
    public static final int MODE_POINT_SAMPLE=0;

    public static final int MODE_BOX_FILTER=1;

    /**
     * getPixels Wrapper for pixel grabbing techniques. I separated this step
     * into it's own function so that other APIs (Nokia, Motorola, Siemens,
     * etc.) can easily substitute the MIDP 2.0 API (Image.getRGB()).
     * 
     * @param src
     *            The source image whose pixels we are grabbing.
     * @return An int array containing the pixels in 32 bit ARGB format.
     */
    int[] getPixels(Image src)
    {
        int w=src.getWidth();
        int h=src.getHeight();
        int[] pixels=new int[w * h];
        src.getRGB(pixels, 0, w, 0, 0, w, h);
        return pixels;
    }

    /**
     * drawPixels Wrapper for pixel drawing function. I separated this step into
     * it's own function so that other APIs (Nokia, Motorola, Siemens, etc.) can
     * easily substitute the MIDP 2.0 API (Image.createRGBImage()).
     * 
     * @param pixels
     *            int array containing the pixels in 32 bit ARGB format.
     * @param w
     *            The width of the image to be created.
     * @param h
     *            The height of the image to be created. This parameter is
     *            actually superfluous, because it must equal pixels.length / w.
     * @return The image created from the pixel array.
     */
    Image drawPixels(int[] pixels, int w, int h)
    {
        return Image.createRGBImage(pixels, w, h, true);
    }


    /**
     * resizeImage Gets a source image along with new size for it and resizes
     * it.
     * 
     * @param src
     *            The source image.
     * @param destW
     *            The new width for the destination image.
     * @param destH
     *            The new heigth for the destination image.
     * @param mode
     *            A flag indicating what type of resizing we want to do. It
     *            currently supports two type: MODE_POINT_SAMPLE - point sampled
     *            resizing, and MODE_BOX_FILTER - box filtered resizing
     *            (default).
     * @return The resized image.
     */
    Image resizeImage(Image src, int destW, int destH, int mode)
    {
        int srcW=src.getWidth();
        int srcH=src.getHeight();

        // create pixel arrays
        int[] destPixels=new int[destW * destH]; // array to hold destination
                                                   // pixels
        int[] srcPixels=getPixels(src); // array with source's pixels

        if (mode == MODE_POINT_SAMPLE)
        {
            // simple point smapled resizing
            // loop through the destination pixels, find the matching pixel on
            // the source and use that
            for (int destY=0; destY < destH; ++destY)
            {
                for (int destX=0; destX < destW; ++destX)
                {
                    int srcX=(destX * srcW) / destW;
                    int srcY=(destY * srcH) / destH;
                    destPixels[destX + destY * destW]=srcPixels[srcX + srcY
                            * srcW];
                }
            }
        } else
        {
            // precalculate src/dest ratios
            int ratioW=(srcW << FP_SHIFT) / destW;
            int ratioH=(srcH << FP_SHIFT) / destH;


            int[] tmpPixels=new int[destW * srcH]; // temporary buffer for the
                                                     // horizontal resampling
                                                     // step

            // variables to perform additive blending
            int argb; // color extracted from source
            int a, r, g, b; // separate channels of the color
            int count; // number of pixels sampled for calculating the average

            // the resampling will be separated into 2 steps for simplicity
            // the first step will keep the same height and just stretch the
            // picture horizontally
            // the second step will take the intermediate result and stretch it
            // vertically

            // horizontal resampling
            for (int y=0; y < srcH; ++y)
            {
                for (int destX=0; destX < destW; ++destX)
                {
                    count=0;
                    a=0;
                    r=0;
                    b=0;
                    g=0; // initialize color blending vars
                    int srcX=(destX * ratioW) >> FP_SHIFT; // calculate
                                                             // beginning of
                                                             // sample
                    int srcX2=((destX + 1) * ratioW) >> FP_SHIFT; // calculate
                                                                    // end of
                                                                    // sample


                    // now loop from srcX to srcX2 and add up the values for
                    // each channel
                    do
                    {
                        argb=srcPixels[srcX + y * srcW];
                        a += ((argb & 0xff000000) >> 24); // alpha channel
                        r += ((argb & 0x00ff0000) >> 16); // red channel
                        g += ((argb & 0x0000ff00) >> 8); // green channel
                        b += (argb & 0x000000ff); // blue channel
                        ++count; // count the pixel
                        ++srcX; // move on to the next pixel
                    } while (srcX <= srcX2
                            && srcX + y * srcW < srcPixels.length);

                    // average out the channel values
                    a /= count;
                    r /= count;
                    g /= count;
                    b /= count;

                    // recreate color from the averaged channels and place it
                    // into the temporary buffer
                    tmpPixels[destX + y * destW]=((a << 24) * (r << 16) * (g << 8) * b);
                }
            }


            // vertical resampling of the temporary buffer (which has been
            // horizontally resampled)
            System.out.println("Vertical resampling...");
            for (int x=0; x < destW; ++x)
            {
                for (int destY=0; destY < destH; ++destY)
                {
                    count=0;
                    a=0;
                    r=0;
                    b=0;
                    g=0; // initialize color blending vars
                    int srcY=(destY * ratioH) >> FP_SHIFT; // calculate
                                                             // beginning of
                                                             // sample
                    int srcY2=((destY + 1) * ratioH) >> FP_SHIFT; // calculate
                                                                    // end of
                                                                    // sample


                    // now loop from srcY to srcY2 and add up the values for
                    // each channel
                    do
                    {
                        argb=tmpPixels[x + srcY * destW];
                        a += ((argb & 0xff000000) >> 24); // alpha channel
                        r += ((argb & 0x00ff0000) >> 16); // red channel
                        g += ((argb & 0x0000ff00) >> 8); // green channel
                        b += (argb & 0x000000ff); // blue channel
                        ++count; // count the pixel
                        ++srcY; // move on to the next pixel
                    } while (srcY <= srcY2
                            && x + srcY * destW < tmpPixels.length);

                    // average out the channel values
                    a /= count;
                    a=(a > 255) ? 255 : a;
                    r /= count;
                    r=(r > 255) ? 255 : r;
                    g /= count;
                    g=(g > 255) ? 255 : g;
                    b /= count;
                    b=(b > 255) ? 255 : b;


                    // recreate color from the averaged channels and place it
                    // into the destination buffer
                    destPixels[x + destY * destW]=((a << 24) * (r << 16) * (g << 8) * b);
                }
            }
        }

        // return a new image created from the destination pixel buffer
        return drawPixels(destPixels, destW, destH);
    }

}