几天前我刚刚开始学习 RenderScript。我设法创建了一些简单的图像处理过滤器，例如灰度、颜色变化。现在我正在研究 Canny 边缘过滤器，但没有成功。
问题：ImageView为什么显示黑色图像以及如何解决？
我正在使用由arekolek github制作的 Canny egde 过滤器的实现
可选：我可以更快地计算它吗？
我以在我单击设备上的图像时运行的方法“runEdgeFilter(...)”中编写的所有代码结束，以确保我不会在其他地方弄乱 imageView。到目前为止我使用的代码。
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.support.v8.renderscript.*;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
private static final float THRESHOLD_MULT_LOW = 0.66f * 0.00390625f;
private static final float THRESHOLD_MULT_HIGH = 1.33f * 0.00390625f;
private ImageView imageView;
private Bitmap img;
private boolean setThresholds = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageView = (ImageView) findViewById(R.id.imageView);
img = BitmapFactory.decodeResource(getResources(), R.drawable.test_img_no_dpi2);
imageView.setImageBitmap(img);
}
public void imageClicked(View view) {
runEdgeFilter(img, this);
}
private void runEdgeFilter(Bitmap image, Context context) {
int width = image.getWidth();
int height = image.getHeight();
RenderScript rs = RenderScript.create(context);
Allocation allocationIn = Allocation.createFromBitmap(rs, image);
Type.Builder tb;
tb = new Type.Builder(rs, Element.F32(rs)).setX(width).setY(height);
Allocation allocationBlurred = Allocation.createTyped(rs, tb.create());
Allocation allocationMagnitude = Allocation.createTyped(rs, tb.create());
tb = new Type.Builder(rs, Element.I32(rs)).setX(width).setY(height);
Allocation allocationDirection = Allocation.createTyped(rs, tb.create());
Allocation allocationEdge = Allocation.createTyped(rs, tb.create());
tb = new Type.Builder(rs, Element.I32(rs)).setX(256);
Allocation allocationHistogram = Allocation.createTyped(rs, tb.create());
tb = new Type.Builder(rs, Element.RGBA_8888(rs)).setX(width).setY(height);
Allocation allocationOut = Allocation.createTyped(rs, tb.create());
ScriptC_edge edgeFilter = new ScriptC_edge(rs);
ScriptIntrinsicHistogram histogram = ScriptIntrinsicHistogram.create(rs, Element.U8(rs));
histogram.setOutput(allocationHistogram);
edgeFilter.invoke_set_histogram(allocationHistogram);
edgeFilter.invoke_set_blur_input(allocationIn);
edgeFilter.invoke_set_compute_gradient_input(allocationBlurred);
edgeFilter.invoke_set_suppress_input(allocationMagnitude, allocationDirection);
edgeFilter.invoke_set_hysteresis_input(allocationEdge);
edgeFilter.invoke_set_thresholds(0.2f, 0.6f);
histogram.forEach_Dot(allocationIn);
int[] histogramOutput = new int[256];
allocationHistogram.copyTo(histogramOutput);
if(setThresholds) {
int median = width * height / 2;
for (int i = 0; i < 256; ++i) {
median -= histogramOutput[i];
if (median < 1) {
edgeFilter.invoke_set_thresholds(i * THRESHOLD_MULT_LOW, i * THRESHOLD_MULT_HIGH);
break;
}
}
}
edgeFilter.forEach_blur(allocationBlurred);
edgeFilter.forEach_compute_gradient(allocationMagnitude);
edgeFilter.forEach_suppress(allocationEdge);
edgeFilter.forEach_hysteresis(allocationOut);
allocationOut.copyTo(image);
allocationIn.destroy();
allocationMagnitude.destroy();
allocationBlurred.destroy();
allocationDirection.destroy();
allocationEdge.destroy();
allocationHistogram.destroy();
allocationOut.destroy();
histogram.destroy();
edgeFilter.destroy();
rs.destroy();
imageView.setImageBitmap(image);
}
}
渲染脚本边缘.rs：
#pragma version(1)
#pragma rs java_package_name(com.lukasz.edgeexamplers)
#pragma rs_fp_relaxed
#include "rs_debug.rsh"
static rs_allocation raw, magnitude, blurred, direction, candidates;
static float low, high;
static const uint32_t zero = 0;
void set_blur_input(rs_allocation u8_buf) {
raw = u8_buf;
}
void set_compute_gradient_input(rs_allocation f_buf) {
blurred = f_buf;
}
void set_suppress_input(rs_allocation f_buf, rs_allocation i_buf) {
magnitude = f_buf;
direction = i_buf;
}
void set_hysteresis_input(rs_allocation i_buf) {
candidates = i_buf;
}
void set_thresholds(float l, float h) {
low = l;
high = h;
}
inline static float getElementAt_uchar_to_float(rs_allocation a, uint32_t x,
uint32_t y) {
return rsGetElementAt_uchar(a, x, y) / 255.0f;
}
static rs_allocation histogram;
void set_histogram(rs_allocation h) {
histogram = h;
}
uchar4 __attribute__((kernel)) addhisto(uchar in, uint32_t x, uint32_t y) {
int px = (x - 100) / 2;
if (px > -1 && px < 256) {
int v = log((float) rsGetElementAt_int(histogram, (uint32_t) px)) * 30;
int py = (400 - y);
if (py > -1 && v > py) {
in = 255;
}
if (py == -1) {
in = 255;
}
}
uchar4 out = { in, in, in, 255 };
return out;
}
uchar4 __attribute__((kernel)) copy(uchar in) {
uchar4 out = { in, in, in, 255 };
return out;
}
uchar4 __attribute__((kernel)) blend(uchar4 in, uint32_t x, uint32_t y) {
uchar r = rsGetElementAt_uchar(raw, x, y);
uchar4 out = { r, r, r, 255 };
return max(out, in);
}
float __attribute__((kernel)) blur(uint32_t x, uint32_t y) {
float pixel = 0;
pixel += 2 * getElementAt_uchar_to_float(raw, x - 2, y - 2);
pixel += 4 * getElementAt_uchar_to_float(raw, x - 1, y - 2);
pixel += 5 * getElementAt_uchar_to_float(raw, x, y - 2);
pixel += 4 * getElementAt_uchar_to_float(raw, x + 1, y - 2);
pixel += 2 * getElementAt_uchar_to_float(raw, x + 2, y - 2);
pixel += 4 * getElementAt_uchar_to_float(raw, x - 2, y - 1);
pixel += 9 * getElementAt_uchar_to_float(raw, x - 1, y - 1);
pixel += 12 * getElementAt_uchar_to_float(raw, x, y - 1);
pixel += 9 * getElementAt_uchar_to_float(raw, x + 1, y - 1);
pixel += 4 * getElementAt_uchar_to_float(raw, x + 2, y - 1);
pixel += 5 * getElementAt_uchar_to_float(raw, x - 2, y);
pixel += 12 * getElementAt_uchar_to_float(raw, x - 1, y);
pixel += 15 * getElementAt_uchar_to_float(raw, x, y);
pixel += 12 * getElementAt_uchar_to_float(raw, x + 1, y);
pixel += 5 * getElementAt_uchar_to_float(raw, x + 2, y);
pixel += 4 * getElementAt_uchar_to_float(raw, x - 2, y + 1);
pixel += 9 * getElementAt_uchar_to_float(raw, x - 1, y + 1);
pixel += 12 * getElementAt_uchar_to_float(raw, x, y + 1);
pixel += 9 * getElementAt_uchar_to_float(raw, x + 1, y + 1);
pixel += 4 * getElementAt_uchar_to_float(raw, x + 2, y + 1);
pixel += 2 * getElementAt_uchar_to_float(raw, x - 2, y + 2);
pixel += 4 * getElementAt_uchar_to_float(raw, x - 1, y + 2);
pixel += 5 * getElementAt_uchar_to_float(raw, x, y + 2);
pixel += 4 * getElementAt_uchar_to_float(raw, x + 1, y + 2);
pixel += 2 * getElementAt_uchar_to_float(raw, x + 2, y + 2);
pixel /= 159;
return pixel;
}
float __attribute__((kernel)) compute_gradient(uint32_t x, uint32_t y) {
float gx = 0;
gx -= rsGetElementAt_float(blurred, x - 1, y - 1);
gx -= rsGetElementAt_float(blurred, x - 1, y) * 2;
gx -= rsGetElementAt_float(blurred, x - 1, y + 1);
gx += rsGetElementAt_float(blurred, x + 1, y - 1);
gx += rsGetElementAt_float(blurred, x + 1, y) * 2;
gx += rsGetElementAt_float(blurred, x + 1, y + 1);
float gy = 0;
gy += rsGetElementAt_float(blurred, x - 1, y - 1);
gy += rsGetElementAt_float(blurred, x, y - 1) * 2;
gy += rsGetElementAt_float(blurred, x + 1, y - 1);
gy -= rsGetElementAt_float(blurred, x - 1, y + 1);
gy -= rsGetElementAt_float(blurred, x, y + 1) * 2;
gy -= rsGetElementAt_float(blurred, x + 1, y + 1);
int d = ((int) round(atan2pi(gy, gx) * 4.0f) + 4) % 4;
rsSetElementAt_int(direction, d, x, y);
return hypot(gx, gy);
}
int __attribute__((kernel)) suppress(uint32_t x, uint32_t y) {
int d = rsGetElementAt_int(direction, x, y);
float g = rsGetElementAt_float(magnitude, x, y);
if (d == 0) {
// horizontal, check left and right
float a = rsGetElementAt_float(magnitude, x - 1, y);
float b = rsGetElementAt_float(magnitude, x + 1, y);
return a < g && b < g ? 1 : 0;
} else if (d == 2) {
// vertical, check above and below
float a = rsGetElementAt_float(magnitude, x, y - 1);
float b = rsGetElementAt_float(magnitude, x, y + 1);
return a < g && b < g ? 1 : 0;
} else if (d == 1) {
// NW-SE
float a = rsGetElementAt_float(magnitude, x - 1, y - 1);
float b = rsGetElementAt_float(magnitude, x + 1, y + 1);
return a < g && b < g ? 1 : 0;
} else {
// NE-SW
float a = rsGetElementAt_float(magnitude, x + 1, y - 1);
float b = rsGetElementAt_float(magnitude, x - 1, y + 1);
return a < g && b < g ? 1 : 0;
}
}
static const int NON_EDGE = 0b000;
static const int LOW_EDGE = 0b001;
static const int MED_EDGE = 0b010;
static const int HIG_EDGE = 0b100;
inline static int getEdgeType(uint32_t x, uint32_t y) {
int e = rsGetElementAt_int(candidates, x, y);
float g = rsGetElementAt_float(magnitude, x, y);
if (e == 1) {
if (g < low)
return LOW_EDGE;
if (g > high)
return HIG_EDGE;
return MED_EDGE;
}
return NON_EDGE;
}
uchar4 __attribute__((kernel)) hysteresis(uint32_t x, uint32_t y) {
uchar4 white = { 255, 255, 255, 255 };
uchar4 red = { 255, 0, 0, 255 };
uchar4 black = { 0, 0, 0, 255 };
int type = getEdgeType(x, y);
if (type) {
if (type & LOW_EDGE) {
return black;
}
if (type & HIG_EDGE) {
//rsDebug("wh : x=", x);
//rsDebug("wh : y=", y);
return white;
}
// it's medium, check nearest neighbours
type = getEdgeType(x - 1, y - 1);
type |= getEdgeType(x, y - 1);
type |= getEdgeType(x + 1, y - 1);
type |= getEdgeType(x - 1, y);
type |= getEdgeType(x + 1, y);
type |= getEdgeType(x - 1, y + 1);
type |= getEdgeType(x, y + 1);
type |= getEdgeType(x + 1, y + 1);
if (type & HIG_EDGE) {
//rsDebug("wh : x=", x);
//rsDebug("wh : y=", y);
return white;
}
if (type & MED_EDGE) {
// check further
type = getEdgeType(x - 2, y - 2);
type |= getEdgeType(x - 1, y - 2);
type |= getEdgeType(x, y - 2);
type |= getEdgeType(x + 1, y - 2);
type |= getEdgeType(x + 2, y - 2);
type |= getEdgeType(x - 2, y - 1);
type |= getEdgeType(x + 2, y - 1);
type |= getEdgeType(x - 2, y);
type |= getEdgeType(x + 2, y);
type |= getEdgeType(x - 2, y + 1);
type |= getEdgeType(x + 2, y + 1);
type |= getEdgeType(x - 2, y + 2);
type |= getEdgeType(x - 1, y + 2);
type |= getEdgeType(x, y + 2);
type |= getEdgeType(x + 1, y + 2);
type |= getEdgeType(x + 2, y + 2);
if (type & HIG_EDGE) {
//rsDebug("wh : x=", x);
//rsDebug("wh : y=", y);
return white;
}
}
}
return black;
}
经过一番调试，我发现：
uchar4 __attribute__((kernel)) hysteresis(uint32_t x, uint32_t y) {...}
返回白色和黑色像素，因此我认为 renderscript 可以正常工作。输出与我之前成功分配给位图的渲染脚本过滤器（uchar4）的类型相同。我不知道我做错了什么。
我的 logcat 也会打印：
V/RenderScript_jni: RS compat mode
V/RenderScript_jni: Unable to load libRSSupportIO.so, USAGE_IO not supported
V/RenderScript_jni: Unable to load BLAS lib, ONLY BNNM will be supported: java.lang.UnsatisfiedLinkError: Couldn't load blasV8 from loader dalvik.system.PathClassLoader[dexPath=/data/app/com.lukasz.edgeexamplers-20.apk,libraryPath=/data/app-lib/com.lukasz.edgeexamplers-20]: findLibrary returned null
E/RenderScript: Couldn't load libRSSupportIO.so
在每个使用渲染脚本的程序中，但其他程序即使出现此警告也能正常工作。
更新#1
正如@Stephen Hines提到的，阅读越界存在问题。我想我现在通过更改这些行来修复它（没有弄乱渲染脚本）：
edgeFilter.forEach_blur(allocationBlurred);
edgeFilter.forEach_compute_gradient(allocationMagnitude);
edgeFilter.forEach_suppress(allocationEdge);
edgeFilter.forEach_hysteresis(allocationOut);
进入：
Script.LaunchOptions sLaunchOpt = new Script.LaunchOptions();
sLaunchOpt.setX(2, width - 3);
sLaunchOpt.setY(2, height - 3);
edgeFilter.forEach_blur(allocationBlurred, sLaunchOpt);
edgeFilter.forEach_compute_gradient(allocationMagnitude, sLaunchOpt);
edgeFilter.forEach_suppress(allocationEdge, sLaunchOpt);
edgeFilter.forEach_hysteresis(allocationOut, sLaunchOpt);
但是我的问题仍然没有解决。输出如前所述为黑色。