Android位图去除白边

Question

我有一个关于 Android 位图的问题:我有一个带有白色边距 [大小未知] 的位图。是否可以创建一个新的位图并删除所有的白色边距(矩形)？

Bitmap bmp = Bitmap.createBitmap(width, bmpheigth, Config.ARGB_8888);
    Canvas canvas = new Canvas(bmp);
    canvas.setBitmap(bmp);
    canvas.drawColor(Color.WHITE);
// draw here things!

假设不知道在哪里画了东西。

这样做的好方法是什么？谢谢!

Answer 1

感谢@Maxim Efimov & @StackOverflowException

以防万一有人需要一个 fragment 来解决这类问题:

此方法返回一个切出的较小的位图，并删除了边距。首先将像素传递给一个 int 数组，然后使用该数组比 Bitmap.getPixel 方法快一点

只需调用指示源位图和背景颜色的方法。

Bitmap bmp2 = removeMargins(bmp, Color.WHITE);


private static Bitmap removeMargins2(Bitmap bmp, int color) {
    // TODO Auto-generated method stub


    long dtMili = System.currentTimeMillis();
    int MTop = 0, MBot = 0, MLeft = 0, MRight = 0;
    boolean found1 = false, found2 = false;

    int[] bmpIn = new int[bmp.getWidth() * bmp.getHeight()];
    int[][] bmpInt = new int[bmp.getWidth()][bmp.getHeight()];

    bmp.getPixels(bmpIn, 0, bmp.getWidth(), 0, 0, bmp.getWidth(),
            bmp.getHeight());

    for (int ii = 0, contX = 0, contY = 0; ii < bmpIn.length; ii++) {
        bmpInt[contX][contY] = bmpIn[ii];
        contX++;
        if (contX >= bmp.getWidth()) {
            contX = 0;
            contY++;
            if (contY >= bmp.getHeight()) {
                break;
            }
        }
    }

    for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
        // looking for MTop
        for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
            if (bmpInt[wP][hP] != color) {
                Log.e("MTop 2", "Pixel found @" + hP);
                MTop = hP;
                found2 = true;
                break;
            }
        }
    }
    found2 = false;

    for (int hP = bmpInt[0].length - 1; hP >= 0 && !found2; hP--) {
        // looking for MBot
        for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
            if (bmpInt[wP][hP] != color) {
                Log.e("MBot 2", "Pixel found @" + hP);
                MBot = bmp.getHeight() - hP;
                found2 = true;
                break;
            }
        }
    }
    found2 = false;

    for (int wP = 0; wP < bmpInt.length && !found2; wP++) {
        // looking for MLeft
        for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
            if (bmpInt[wP][hP] != color) {
                Log.e("MLeft 2", "Pixel found @" + wP);
                MLeft = wP;
                found2 = true;
                break;
            }
        }
    }
    found2 = false;

    for (int wP = bmpInt.length - 1; wP >= 0 && !found2; wP--) {
        // looking for MRight
        for (int hP = 0; hP < bmpInt[0].length && !found2; hP++) {
            if (bmpInt[wP][hP] != color) {
                Log.e("MRight 2", "Pixel found @" + wP);
                MRight = bmp.getWidth() - wP;
                found2 = true;
                break;
            }
        }

    }
    found2 = false;

    int sizeY = bmp.getHeight() - MBot - MTop, sizeX = bmp.getWidth()
            - MRight - MLeft;

    Bitmap bmp2 = Bitmap.createBitmap(bmp, MLeft, MTop, sizeX, sizeY);
    dtMili = (System.currentTimeMillis() - dtMili);
    Log.e("Margin   2",
            "Time needed " + dtMili + "mSec\nh:" + bmp.getWidth() + "w:"
                    + bmp.getHeight() + "\narray x:" + bmpInt.length + "y:"
                    + bmpInt[0].length);
    return bmp2;
}