由于Robot.createScreenCaputure()方法很慢，我决定使用本机库。我搜索并找到了这个forum并找到了一个使用 JNA Library 的特定code snipplet。这是一个旧版本，所以我重写了代码：
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferInt;
import java.awt.image.DataBufferUShort;
import java.awt.image.DirectColorModel;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import com.sun.jna.Native;
import com.sun.jna.win32.W32APIOptions;
import com.sun.jna.platform.win32.WinDef;
import com.sun.jna.platform.win32.WinNT;
import com.sun.jna.platform.win32.WinGDI;
public class JNAScreenShot {
public static BufferedImage getScreenshot(Rectangle bounds) {
WinDef.HDC windowDC = GDI.GetDC(USER.GetDesktopWindow());
WinDef.HBITMAP outputBitmap =
GDI.CreateCompatibleBitmap(windowDC,
bounds.width, bounds.height);
try {
WinDef.HDC blitDC = GDI.CreateCompatibleDC(windowDC);
try {
WinNT.HANDLE oldBitmap =
GDI.SelectObject(blitDC, outputBitmap);
try {
GDI.BitBlt(blitDC,
0, 0, bounds.width, bounds.height,
windowDC,
bounds.x, bounds.y,
GDI32.SRCCOPY);
} finally {
GDI.SelectObject(blitDC, oldBitmap);
}
WinGDI.BITMAPINFO bi = new WinGDI.BITMAPINFO(40);
bi.bmiHeader.biSize = 40;
boolean ok =
GDI.GetDIBits(blitDC, outputBitmap, 0, bounds.height,
(byte[]) null, bi, WinGDI.DIB_RGB_COLORS);
if (ok) {
WinGDI.BITMAPINFOHEADER bih = bi.bmiHeader;
bih.biHeight = -Math.abs(bih.biHeight);
bi.bmiHeader.biCompression = 0;
return bufferedImageFromBitmap(blitDC, outputBitmap, bi);
} else {
return null;
}
} finally {
GDI.DeleteObject(blitDC);
}
} finally {
GDI.DeleteObject(outputBitmap);
}
}
private static BufferedImage bufferedImageFromBitmap(WinDef.HDC blitDC,
WinDef.HBITMAP outputBitmap,
WinGDI.BITMAPINFO bi) {
WinGDI.BITMAPINFOHEADER bih = bi.bmiHeader;
int height = Math.abs(bih.biHeight);
final ColorModel cm;
final DataBuffer buffer;
final WritableRaster raster;
int strideBits =
(bih.biWidth * bih.biBitCount);
int strideBytesAligned =
(((strideBits - 1) | 0x1F) + 1) >> 3;
final int strideElementsAligned;
switch (bih.biBitCount) {
case 16:
strideElementsAligned = strideBytesAligned / 2;
cm = new DirectColorModel(16, 0x7C00, 0x3E0, 0x1F);
buffer =
new DataBufferUShort(strideElementsAligned * height);
raster =
Raster.createPackedRaster(buffer,
bih.biWidth, height,
strideElementsAligned,
((DirectColorModel) cm).getMasks(),
null);
break;
case 32:
strideElementsAligned = strideBytesAligned / 4;
cm = new DirectColorModel(32, 0xFF0000, 0xFF00, 0xFF);
buffer =
new DataBufferInt(strideElementsAligned * height);
raster =
Raster.createPackedRaster(buffer,
bih.biWidth, height,
strideElementsAligned,
((DirectColorModel) cm).getMasks(),
null);
break;
default:
throw new IllegalArgumentException("Unsupported bit count: " + bih.biBitCount);
}
final boolean ok;
switch (buffer.getDataType()) {
case DataBuffer.TYPE_INT: {
int[] pixels = ((DataBufferInt) buffer).getData();
ok = GDI.GetDIBits(blitDC, outputBitmap, 0, raster.getHeight(), pixels, bi, 0);
}
break;
case DataBuffer.TYPE_USHORT: {
short[] pixels = ((DataBufferUShort) buffer).getData();
ok = GDI.GetDIBits(blitDC, outputBitmap, 0, raster.getHeight(), pixels, bi, 0);
}
break;
default:
throw new AssertionError("Unexpected buffer element type: " + buffer.getDataType());
}
if (ok) {
return new BufferedImage(cm, raster, false, null);
} else {
return null;
}
}
private static final User32 USER = User32.INSTANCE;
private static final GDI32 GDI = GDI32.INSTANCE;
}
interface GDI32 extends com.sun.jna.platform.win32.GDI32,
com.sun.jna.platform.win32.WinGDI,
com.sun.jna.platform.win32.WinDef {
GDI32 INSTANCE =
(GDI32) Native.loadLibrary(GDI32.class);
boolean BitBlt(HDC hdcDest, int nXDest, int nYDest,
int nWidth, int nHeight, HDC hdcSrc,
int nXSrc, int nYSrc, int dwRop);
HDC GetDC(HWND hWnd);
boolean GetDIBits(HDC dc, HBITMAP bmp, int startScan, int scanLines,
byte[] pixels, BITMAPINFO bi, int usage);
boolean GetDIBits(HDC dc, HBITMAP bmp, int startScan, int scanLines,
short[] pixels, BITMAPINFO bi, int usage);
boolean GetDIBits(HDC dc, HBITMAP bmp, int startScan, int scanLines,
int[] pixels, BITMAPINFO bi, int usage);
int SRCCOPY = 0xCC0020;
}
interface User32 extends com.sun.jna.platform.win32.User32 {
User32 INSTANCE = (User32) Native.loadLibrary(User32.class, W32APIOptions.UNICODE_OPTIONS);
com.sun.jna.platform.win32.WinDef.HWND GetDesktopWindow();
}
一个测试代码，用于查看比Robot Class更快：
import java.awt.AWTException;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.image.BufferedImage;
public class testClass {
public static void main(String[] args) {
BufferedImage bi = null, bj = null;
Rectangle rect = new Rectangle(0, 0, 810, 384);
long startTime, finishTime;
startTime = System.currentTimeMillis();
for (int i = 0; i < 10; i++) {
bi = JNAScreenShot.getScreenshot(rect);
}
finishTime = System.currentTimeMillis();
System.out.println("With JNA Library: " + (finishTime - startTime)/10);
Robot robo = null;
startTime = System.currentTimeMillis();
try {
robo = new Robot();
} catch (AWTException a) {
}
for (int i = 0; i < 10; i++) {
bj = robo.createScreenCapture(rect);
}
finishTime = System.currentTimeMillis();
System.out.println("With Robot Class " + (finishTime - startTime)/10);
}
}
结果是
使用JNA Library：77
使用Robot Class 37
伙计们，有人解释为什么是这样，如何我可以把它固定下来？
答案 0 :(得分：5)
不要试图过早优化。创建一个合理的界面来获取您想要的数据（截图）然后根据Robot，JNA或JNI创建您想要的实现。
我猜这些不同的实现会根据它运行的环境给出完全不同的结果。
编程规则之一：首先让它发挥作用。然后进行配置，发现瓶颈并消除或减轻瓶颈的影响。
答案 1 :(得分：0)
首先，检查本机库是否实际上比您的代码更快。可能不是这样。
假设你已经检查过，我会说这里的问题是用JNA调用真的很慢。 要跳过每个周期一次调用问题，我建议编写一个这样的C函数：
void callWithJNAfunction(int rectPosX, int rectPosY, rectSideX, rectSideY,int numberOfCycles) {
for (int i = 0; i < numberOfCycles; i++) {
//code in C that calls the library
}
现在编译此代码并使用JNA调用callWithJNAfunction（...）。
如果问题是JNA调用缓慢，它会变快。
答案 2 :(得分：0)
JNA调用需要很长时间，而JNI直接使用c ++。