/**

* 素描效果

*

* @param bmp

* @return

*/

public static Bitmap convertToSketch(Bitmap bmp) {

int pos, row, col, clr;

int width = bmp.getWidth();

int height = bmp.getHeight();

int[] pixSrc = new int[width * height];

int[] pixNvt = new int[width * height];

// 先对图象的像素处理成灰度颜色后再取反

bmp.getPixels(pixSrc, 0, width, 0, 0, width, height);

for (row = 0; row < height; row++) {

for (col = 0; col < width; col++) {

pos = row * width + col;

pixSrc[pos] = (Color.red(pixSrc[pos])

+ Color.green(pixSrc[pos]) + Color.blue(pixSrc[pos])) / 3;

pixNvt[pos] = 255 - pixSrc[pos];

}

}

// 对取反的像素进行高斯模糊, 强度可以设置，暂定为5.0

gaussGray(pixNvt, 5.0, 5.0, width, height);

// 灰度颜色和模糊后像素进行差值运算

for (row = 0; row < height; row++) {

for (col = 0; col < width; col++) {

pos = row * width + col;

clr = pixSrc[pos] << 8;

clr /= 256 - pixNvt[pos];

clr = Math.min(clr, 255);

pixSrc[pos] = Color.rgb(clr, clr, clr);

}

}

bmp.setPixels(pixSrc, 0, width, 0, 0, width, height);

return bmp;

}

private static int gaussGray(int[] psrc, double horz, double vert,

int width, int height) {

int[] dst, src;

double[] n_p, n_m, d_p, d_m, bd_p, bd_m;

double[] val_p, val_m;

int i, j, t, k, row, col, terms;

int[] initial_p, initial_m;

double std_dev;

int row_stride = width;

int max_len = Math.max(width, height);

int sp_p_idx, sp_m_idx, vp_idx, vm_idx;

val_p = new double[max_len];

val_m = new double[max_len];

n_p = new double[5];

n_m = new double[5];

d_p = new double[5];

d_m = new double[5];

bd_p = new double[5];

bd_m = new double[5];

src = new int[max_len];

dst = new int[max_len];

initial_p = new int[4];

initial_m = new int[4];

// 垂直方向

if (vert > 0.0) {

vert = Math.abs(vert) + 1.0;

std_dev = Math.sqrt(-(vert * vert) / (2 * Math.log(1.0 / 255.0)));

// 初试化常量

findConstants(n_p, n_m, d_p, d_m, bd_p, bd_m, std_dev);

for (col = 0; col < width; col++) {

for (k = 0; k < max_len; k++) {

val_m[k] = val_p[k] = 0;

}

for (t = 0; t < height; t++) {

src[t] = psrc[t * row_stride + col];

}

sp_p_idx = 0;

sp_m_idx = height - 1;

vp_idx = 0;

vm_idx = height - 1;

initial_p[0] = src[0];

initial_m[0] = src[height - 1];

for (row = 0; row < height; row++) {

terms = (row < 4) ? row : 4;

for (i = 0; i <= terms; i++) {

val_p[vp_idx] += n_p[i] * src[sp_p_idx - i] - d_p[i]

* val_p[vp_idx - i];

val_m[vm_idx] += n_m[i] * src[sp_m_idx + i] - d_m[i]

* val_m[vm_idx + i];

}

for (j = i; j <= 4; j++) {

val_p[vp_idx] += (n_p[j] - bd_p[j]) * initial_p[0];

val_m[vm_idx] += (n_m[j] - bd_m[j]) * initial_m[0];

}

sp_p_idx++;

sp_m_idx--;

vp_idx++;

vm_idx--;

}

transferGaussPixels(val_p, val_m, dst, 1, height);

for (t = 0; t < height; t++) {

psrc[t * row_stride + col] = dst[t];

}

}

}

// 水平方向

if (horz > 0.0) {

horz = Math.abs(horz) + 1.0;

if (horz != vert) {

std_dev = Math.sqrt(-(horz * horz)

/ (2 * Math.log(1.0 / 255.0)));

// 初试化常量

findConstants(n_p, n_m, d_p, d_m, bd_p, bd_m, std_dev);

}

for (row = 0; row < height; row++) {

for (k = 0; k < max_len; k++) {

val_m[k] = val_p[k] = 0;

}

for (t = 0; t < width; t++) {

src[t] = psrc[row * row_stride + t];

}

sp_p_idx = 0;

sp_m_idx = width - 1;

vp_idx = 0;

vm_idx = width - 1;

initial_p[0] = src[0];

initial_m[0] = src[width - 1];

for (col = 0; col < width; col++) {

terms = (col < 4) ? col : 4;

for (i = 0; i <= terms; i++) {

val_p[vp_idx] += n_p[i] * src[sp_p_idx - i] - d_p[i]

* val_p[vp_idx - i];

val_m[vm_idx] += n_m[i] * src[sp_m_idx + i] - d_m[i]

* val_m[vm_idx + i];

}

for (j = i; j <= 4; j++) {

val_p[vp_idx] += (n_p[j] - bd_p[j]) * initial_p[0];

val_m[vm_idx] += (n_m[j] - bd_m[j]) * initial_m[0];

}

sp_p_idx++;

sp_m_idx--;

vp_idx++;

vm_idx--;

}

transferGaussPixels(val_p, val_m, dst, 1, width);

for (t = 0; t < width; t++) {

psrc[row * row_stride + t] = dst[t];

}

}

}

return 0;

}

private static void transferGaussPixels(double[] src1, double[] src2,

int[] dest, int bytes, int width) {

int i, j, k, b;

int bend = bytes * width;

double sum;

i = j = k = 0;

for (b = 0; b < bend; b++) {

sum = src1[i++] + src2[j++];

if (sum > 255)

sum = 255;

else if (sum < 0)

sum = 0;

dest[k++] = (int) sum;

}

}

private static void findConstants(double[] n_p, double[] n_m, double[] d_p,

double[] d_m, double[] bd_p, double[] bd_m, double std_dev) {

double div = Math.sqrt(2 * 3.141593) * std_dev;

double x0 = -1.783 / std_dev;

double x1 = -1.723 / std_dev;

double x2 = 0.6318 / std_dev;

double x3 = 1.997 / std_dev;

double x4 = 1.6803 / div;

double x5 = 3.735 / div;

double x6 = -0.6803 / div;

double x7 = -0.2598 / div;

int i;

n_p[0] = x4 + x6;

n_p[1] = (Math.exp(x1)

* (x7 * Math.sin(x3) - (x6 + 2 * x4) * Math.cos(x3)) + Math

.exp(x0) * (x5 * Math.sin(x2) - (2 * x6 + x4) * Math.cos(x2)));

n_p[2] = (2

* Math.exp(x0 + x1)

* ((x4 + x6) * Math.cos(x3) * Math.cos(x2) - x5 * Math.cos(x3)

* Math.sin(x2) - x7 * Math.cos(x2) * Math.sin(x3)) + x6

* Math.exp(2 * x0) + x4 * Math.exp(2 * x1));

n_p[3] = (Math.exp(x1 + 2 * x0)

* (x7 * Math.sin(x3) - x6 * Math.cos(x3)) + Math.exp(x0 + 2

* x1)

* (x5 * Math.sin(x2) - x4 * Math.cos(x2)));

n_p[4] = 0.0;

d_p[0] = 0.0;

d_p[1] = -2 * Math.exp(x1) * Math.cos(x3) - 2 * Math.exp(x0)

* Math.cos(x2);

d_p[2] = 4 * Math.cos(x3) * Math.cos(x2) * Math.exp(x0 + x1)

+ Math.exp(2 * x1) + Math.exp(2 * x0);

d_p[3] = -2 * Math.cos(x2) * Math.exp(x0 + 2 * x1) - 2 * Math.cos(x3)

* Math.exp(x1 + 2 * x0);

d_p[4] = Math.exp(2 * x0 + 2 * x1);

for (i = 0; i <= 4; i++) {

d_m[i] = d_p[i];

}

n_m[0] = 0.0;

for (i = 1; i <= 4; i++) {

n_m[i] = n_p[i] - d_p[i] * n_p[0];

}

double sum_n_p, sum_n_m, sum_d;

double a, b;

sum_n_p = 0.0;

sum_n_m = 0.0;

sum_d = 0.0;

for (i = 0; i <= 4; i++) {

sum_n_p += n_p[i];

sum_n_m += n_m[i];

sum_d += d_p[i];

}

a = sum_n_p / (1.0 + sum_d);

b = sum_n_m / (1.0 + sum_d);

for (i = 0; i <= 4; i++) {

bd_p[i] = d_p[i] * a;

bd_m[i] = d_m[i] * b;

}

}