在Windows上运行的一些Java代码中,我正在从磁盘读取一些大块RGB数据,并希望尽快将其显示在屏幕上。 RGB数据是每通道8位,没有任何alpha。目前我有以下代码来创建BufferedImage。
BufferedImage getBufferedImage(File file, int width, int height) {
byte[] rgbData = readRGBFromFile(file);
WritableRaster raster = Raster.createInterleavedRaster(
rgbData, width, height,
width * 3, // scanlineStride
3, // pixelStride
new int[]{0, 1, 2}, // bandOffsets
null);
ColorModel colorModel = new ComponentColorModel(
ColorSpace.getInstance(ColorSpace.CS_sRGB),
new int[]{8, 8, 8}, // bits
false, // hasAlpha
false, // isPreMultiplied
ComponentColorModel.OPAQUE,
DataBuffer.TYPE_BYTE);
return new BufferedImage(colorModel, raster, false, null);
}
问题是将此渲染到屏幕的性能非常慢。大约250 - 300毫秒。我已经读过,为了获得最佳性能,您需要在与屏幕兼容的BufferedImage中显示。为此,我将从上述方法返回的缓冲图像传递给这样的方法。
BufferedImage createCompatibleImage(BufferedImage image)
{
GraphicsConfiguration gc = GraphicsEnvironment.
getLocalGraphicsEnvironment().
getDefaultScreenDevice().
getDefaultConfiguration();
BufferedImage newImage = gc.createCompatibleImage(
image.getWidth(),
image.getHeight(),
Transparency.TRANSLUCENT);
Graphics2D g = newImage.createGraphics();
g.drawImage(image, 0, 0, null);
g.dispose();
return newImage;
}
该方法在Windows上实质上将其从RGB转换为ARGB,并且它确实加快了显示速度,但对于1600 x 1200 RGB数据块,此方法需要约300 ms。所以现在我基本上将绘图问题的性能影响转换为转换问题。
300ms与从磁盘加载RGB数据的时间差不多。我想我可以做得更快。
我有更好的方式进行转换吗?或者,如果我事先修改了RGB数据并添加了alpha通道,它会有帮助吗?如果是这样,我的Raster和ColorModel会是什么样子。此外,由于我的RGB数据不包含透明度,我可以通过使用预乘的alpha或其他东西来获得任何性能改进吗?
对不起,我在这个ColorModel,Raster的东西上有点迷失。
谢谢!
答案 0 :(得分:20)
我意识到这是一个非常古老的问题,我只是将其发布给任何可能偶然发现这个问题寻找更多选择的人。我最近遇到了一个问题,我试图获取一个大的(720p)RGB字节[]并将其渲染为BufferedImage
。我使用的原始实现看起来像这样(在这里简化):
public void processFrame(byte[] frame, int width, int height)
{
DataBuffer videoBuffer = new DataBufferByte(frame,frame.length);
BufferedImage currentImage = new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
ComponentSampleModel sampleModel = new ComponentSampleModel(DataBuffer.TYPE_BYTE,width,height,3,width*3,new int[] {2,1,0});
Raster raster = Raster.createRaster(sampleModel,videoBuffer,null);
currentImage.setData(raster);
}
即使有一次优化,例如创建BufferedImage
和ComponentSampleModel
并重复使用它们,在setData
上调用BufferedImage
的最后一步仍然是大约50 -60毫秒,这是不可接受的。
我最终意识到,至少对于我的场景,你实际上可以直接写入BufferedImage
的后备字节数组并绕过大部分中间处理(假设图像的后备元数据是已经正确)。所以我将代码更改为:
public void processFrame(byte[] frame, int width, int height)
{
BufferedImage currentImage = new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
byte[] imgData = ((DataBufferByte)currentImage.getRaster().getDataBuffer()).getData();
System.arraycopy(frame,0,imgData,0,frame.length);
}
通过这样做,我的性能提高了大约20倍。我现在在3-5毫秒而不是50-60毫秒内处理相同的帧。
这可能不适用于所有情况,但我认为我会分享以防其他人认为它有用。
答案 1 :(得分:11)
在玩完这个后,如果当前的图形配置使用ARGB整数打包栅格,我有一个适合Windows的答案。
我首先创建兼容的BufferedImage,然后手动将我的RGB字节数组转换为ARGB int数组。然后我从兼容的BufferedImage中获取Raster并将我的ARGB注入其中。这要快得多。
我还有一个类,用于检查兼容的BufferedImage是否采用我期望的格式,如果不是,则默认使用较旧的较慢方法。
这是班级。希望它能帮到你。
/**
* This class can read chunks of RGB image data out of a file and return a BufferedImage.
* It may use an optimized technique for loading images that relies on assumptions about the
* default image format on Windows.
*/
public class RGBImageLoader
{
private byte[] tempBuffer_;
private boolean fastLoading_;
public RGBImageLoader()
{
fastLoading_ = canUseFastLoadingTechnique();
}
private boolean canUseFastLoadingTechnique()
{
// Create an image that's compatible with the screen
GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(100, 100, Transparency.TRANSLUCENT);
// On windows this should be an ARGB integer packed raster. If it is then we can
// use our optimization technique
if(image.getType() != BufferedImage.TYPE_INT_ARGB)
return false;
WritableRaster raster = image.getRaster();
if(!(raster instanceof IntegerInterleavedRaster))
return false;
if(!(raster.getDataBuffer() instanceof DataBufferInt))
return false;
if(!(image.getColorModel() instanceof DirectColorModel))
return false;
DirectColorModel colorModel = (DirectColorModel) image.getColorModel();
if(!(colorModel.getColorSpace() instanceof ICC_ColorSpace) ||
colorModel.getNumComponents() != 4 ||
colorModel.getAlphaMask() != 0xff000000 ||
colorModel.getRedMask() != 0xff0000 ||
colorModel.getGreenMask() != 0xff00 ||
colorModel.getBlueMask() != 0xff)
return false;
if(raster.getNumBands() != 4 ||
raster.getNumDataElements() != 1 ||
!(raster.getSampleModel() instanceof SinglePixelPackedSampleModel))
return false;
return true;
}
public BufferedImage loadImage(File file, int width, int height, long imageOffset) throws IOException
{
if(fastLoading_)
return loadImageUsingFastTechnique(file, width, height, imageOffset);
else
return loadImageUsingCompatibleTechnique(file, width, height, imageOffset);
}
private BufferedImage loadImageUsingFastTechnique(File file, int width, int height, long imageOffset) throws IOException
{
int sizeBytes = width * height * 3;
// Make sure buffer is big enough
if(tempBuffer_ == null || tempBuffer_.length < sizeBytes)
tempBuffer_ = new byte[sizeBytes];
RandomAccessFile raf = null;
try
{
raf = new RandomAccessFile(file, "r");
raf.seek(imageOffset);
int bytesRead = raf.read(tempBuffer_, 0, sizeBytes);
if (bytesRead != sizeBytes)
throw new IOException("Invalid byte count. Should be " + sizeBytes + " not " + bytesRead);
GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(width, height, Transparency.TRANSLUCENT);
WritableRaster raster = image.getRaster();
DataBufferInt dataBuffer = (DataBufferInt) raster.getDataBuffer();
addAlphaChannel(tempBuffer_, sizeBytes, dataBuffer.getData());
return image;
}
finally
{
try
{
if(raf != null)
raf.close();
}
catch(Exception ex)
{
}
}
}
private BufferedImage loadImageUsingCompatibleTechnique(File file, int width, int height, long imageOffset) throws IOException
{
int sizeBytes = width * height * 3;
RandomAccessFile raf = null;
try
{
raf = new RandomAccessFile(file, "r");
// Lets navigate to the offset
raf.seek(imageOffset);
DataBufferByte dataBuffer = new DataBufferByte(sizeBytes);
byte[] bytes = dataBuffer.getData();
int bytesRead = raf.read(bytes, 0, sizeBytes);
if (bytesRead != sizeBytes)
throw new IOException("Invalid byte count. Should be " + sizeBytes + " not " + bytesRead);
WritableRaster raster = Raster.createInterleavedRaster(dataBuffer, // dataBuffer
width, // width
height, // height
width * 3, // scanlineStride
3, // pixelStride
new int[]{0, 1, 2}, // bandOffsets
null); // location
ColorModel colorModel = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_sRGB), // ColorSpace
new int[]{8, 8, 8}, // bits
false, // hasAlpha
false, // isPreMultiplied
ComponentColorModel.OPAQUE, DataBuffer.TYPE_BYTE);
BufferedImage loadImage = new BufferedImage(colorModel, raster, false, null);
// Convert it into a buffered image that's compatible with the current screen.
// Not ideal creating this image twice....
BufferedImage image = createCompatibleImage(loadImage);
return image;
}
finally
{
try
{
if(raf != null)
raf.close();
}
catch(Exception ex)
{
}
}
}
private BufferedImage createCompatibleImage(BufferedImage image)
{
GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
BufferedImage newImage = gc.createCompatibleImage(image.getWidth(), image.getHeight(), Transparency.TRANSLUCENT);
Graphics2D g = newImage.createGraphics();
g.drawImage(image, 0, 0, null);
g.dispose();
return newImage;
}
private void addAlphaChannel(byte[] rgbBytes, int bytesLen, int[] argbInts)
{
for(int i=0, j=0; i<bytesLen; i+=3, j++)
{
argbInts[j] = ((byte) 0xff) << 24 | // Alpha
(rgbBytes[i] << 16) & (0xff0000) | // Red
(rgbBytes[i+1] << 8) & (0xff00) | // Green
(rgbBytes[i+2]) & (0xff); // Blue
}
}
}