从QImage获取原始数据 [英] Get raw data from QImage

问题描述

我有一个QImage，我从一个像素图建立一个像下面的：

  QPixmap fullPmap = topItem-& （）; 
 fullPmap = fullPmap.copy（isec.toRect（））; 
 QImage chip = fullPmap.toImage（）; 
  

这基本上与屏幕上的矩形相交，以将图像裁切为大小不一的图像。 >

我现在需要获取表示从芯片返回的数据的字符数组。

我该如何做？

我试过这样：

  unsigned char * data = chip.bits（）; 
  

当我显示数据时，我得到一个完全失真的图像， / p>

fullPmap是一个RGB图像，如果这很重要。我有一些代码，我使用它将其转换为灰度：

  QRgb col 
 int gray; 
 for（int i = 0; i  {
 for（int j = 0; j  {
 col = chip.pixel（i，j）; 
 gray = qGray（col）; 
 chip.setPixel（i，j，qRgb（gray，gray，gray））; 
} 
} 
  

我不太喜欢，

显示从bits（）返回的数据如下所示：

  imwidth = chip.width（）; 
 imheight = chip.height（）; 
 QImage * qi = new QImage（imwidth，imheight，QImage :: Format_RGB32）; 
 // #pragma omp parallel for 
 for（int i = 0; i  for（int j = 0; j< imwidth; j ++）
 {
 qi-> setPixel（j，i，qRgb（data [i * imwidth + j]，data [i * imwidth + j]，data [i * imwidth + j] 
} 
  

解决方案

，您需要注意一些基本问题：

• 像素
  数据的格式或布局是什么。从
  转换的QImage QPixmap不一定总是在
  RGB888或RGB32。调用
  QImage :: format（）并处理
  不同的布局。
  特别是对于RGB32系列，
  需要确保以
  右字节顺序（endian）访问它们。




• 字节不总是布局
  正好是许多字节来保存
  像素的行。通常，
  行比
  需要更多的字节。使用QImage :: bytesPerLine（）到
  找到并推进指针
  ，当到
  下一行时，许多字节。这可能是您在显示图片建立中的问题
  。




• QImage :: pixel（）和setPixel真的慢。如果可能，从原始像素缓冲区获取/设置像素值
  。

I have a QImage that I built from a pixmap something like the following:

QPixmap fullPmap = topItem->pixmap();
fullPmap = fullPmap.copy(isec.toRect());
QImage chip = fullPmap.toImage();

This is basically intersecting with a rectangle on screen to crop the image to a chipped size.

I now need to get the character array representing that data back from chip.

How can I do this?

I tried something like this:

  unsigned char * data = chip.bits();

And when I display "data" I get a completely distorted image, nothing like my actual chip.

fullPmap is an RGB image if that matters. I have some code that I am using to convert it to grayscale:

QRgb col;
int gray;
for (int i = 0; i < chip.width(); ++i)
{
    for (int j = 0; j < chip.height(); ++j)
    {
        col = chip.pixel(i, j);
        gray = qGray(col);
        chip.setPixel(i, j, qRgb(gray, gray, gray));
    }
}

Which I don't really like, but it seemed like the easiest way to do such a thing.

Displaying the data that is returned from bits() looks like this:

imwidth = chip.width();
imheight = chip.height();
QImage *qi = new QImage(imwidth, imheight, QImage::Format_RGB32);
//  #pragma omp parallel for
for (int i = 0 ; i < imheight ; i++)
    for (int j = 0 ; j < imwidth ; j++)
    {
        qi->setPixel(j,i,qRgb(data[i*imwidth + j],data[i*imwidth + j],data[i*imwidth + j]));
    }

解决方案

When dealing with raw image data, you need to be aware of some basic issues:

• What is the format or layout of pixel data. The QImage converted from QPixmap is not necessarily always in RGB888 or RGB32. Call QImage::format() and deal with different layout differently. Especially with RGB32 family, you need to make sure you access them in right byte order (endian).

• The bytes are not always layout exactly that many bytes to hold the pixels of the line. Typically a line will have more bytes than it's needed. Use QImage::bytesPerLine() to find out and advance the pointer by that many bytes when going to the next line. This is probably your issue in the building of the display image.

• QImage::pixel() and setPixel() are really slow. Get/set pixel values from raw pixel buffer if possible.

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