java.lang.Stackoverflowerror: stack size 1038KB

Question

I’m making an algorithm that converts one bitmap leaving it in shades of gray.

I could do it using for but I’d like to do it recursively.

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Using for (This working well)

//BUTTON - ON CLICK . . .
public void go(View v){
    //BM_3 É UM BITMAP, VARIAVEL GLOBAL QUE JÁ POSSUI UMA IMAGEM EM SEU CONTEUDO . . .
    bm_3 = bm_3.copy(Bitmap.Config.ARGB_8888, true);

    for (int x = 0; x < bm_3.getWidth(); x++){
        for (int y = 0; y < bm_3.getHeight(); y++) {

            String hex = Integer.toHexString(bm_3.getPixel(x, y));

            if(hex.length() == 8) {
                String hexX = "#" + convert_Hex_to_grey("" + hex.charAt(0) + hex.charAt(1),
                                                        "" + hex.charAt(2) + hex.charAt(3),
                                                        "" + hex.charAt(4) + hex.charAt(5),
                                                        "" + hex.charAt(6) + hex.charAt(7));

                bm_3.setPixel(x, y, Color.parseColor(hexX));
            }
        }
    }
    //IMG É UMA IMAGEVIEW . . .
    img.setImageBitmap(bm_3);
}

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Based on the above algorithm, I have tried to implement it recursively. However, it shows error of java.lang.StackOverflowError: stack size 1038KB

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Using recursion (java.lang.Stackoverflowerror)

RECURSION

private Bitmap grey_scale(int x, int y, Bitmap bm_3) {
        //IF PARA PERCORRER TODO Y . . .
        if (y < bm_3.getHeight()) {
            String hex = Integer.toHexString(bm_3.getPixel(x, y));
            if (hex.length() == 8) {
                String hexX = "#" + convert_Hex_to_grey("" + hex.charAt(0) + hex.charAt(1),
                                                        "" + hex.charAt(2) + hex.charAt(3),
                                                        "" + hex.charAt(4) + hex.charAt(5),
                                                        "" + hex.charAt(6) + hex.charAt(7));


                bm_3.setPixel(x, y, Color.parseColor(hexX));
            }
            //O ERRO OCORRE NESTE RETURN ! ! !
            return grey_scale(x, y+1, bm_3);

        }
        //IF PARA PERCORRER TODO X, ZERANDO Y A CADA TROCA DE X.
        if (x < bm_3.getWidth()) {
            return grey_scale(x+1, 0, bm_3);
        }
    //RETORNA BITMAP
    return bm_3;
}

BUTTON ON CLICK CALLING RECURSION

public void go(View v){

    bm_3 = bm_3.copy(Bitmap.Config.ARGB_8888, true);
    //FAZ RECURSAO DENTRO DE UMA THREAD . . .
    new Thread(new Runnable() {
        @Override
        public void run() {
            //CHAMA A RECURSAO
            bm_3 = grey_scale(0, 0, bm_3);

            //VOLTA PRA THREAD PRINCIPAL PARA ATUALIZAR O IMAGEVIEW . . .
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    img.setImageBitmap(bm_3);
                }
            });
        }
    }).start();
}

Answer 1

The problem here is the recursion size. Its recursion is approximately 621,000 calls, given the 788 x 788 image.

Each recursive call at least inserts the call arguments into the stack. In this case, there are two integers and a reference; the integers are 4 bytes each, the reference is 8 or 4 bytes (8 bytes for 64 bits and 4 bytes for 32 bits). So you put at least 12 bytes for each recursive call. Thus, not considering other factors, the minimum required for the stack is 10 or 12 megabytes of only recursive call arguments. Who knows how much more of other information?

Anyway, maybe with 64 megabytes of stack? To determine this value, the virtual machine argument -Xss 64M defines that. Source

Well, AP is having the problem running on Android Studio, so try to do these tweaks with the JVM may not result in anything.

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PS: Just before I finished writing this answer, I saw that setting the size of the stack in the thread did not work. I’ll inspect a little longer and then edit the answer with whatever I find