Qt中的线插值？

Question

我试图通过除去线的长度来减少画笔笔划的间距(在QPixmap上).如果我乘以线,则间距增加,但间距不会减小.此外,线条可以具有的最小长度为1.显然划分它会减少 - 可能低于允许的数量？不确定这是否会对像素图的绘制产生负面影响.

这是违规代码:

QLineF line = QLineF(lastPoint, endPoint);
float lineLength = line.length();
qDebug() << line.length();
line.setLength(lineLength / 50.0f);
qDebug() << line.length();

painter.drawPixmap(line.p1().x() - 16, line.p2().y() - 16, 32, 32, testPixmap);

以下是此特定文件中的所有代码:

#include "inkspot.h"
#include "inkpuppet.h"
#include "ui_inkpuppet.h"

#include "newdialog.h"
#include "ui_newdialog.h"

#include <QtCore>
#include <QtGui>
#include <QWidget>
#include <QPainter>
#include <QPaintEvent>

InkSpot::InkSpot(QWidget *parent) :
    QWidget(parent)
{
    widget = this;
    drawing = false;
}

void InkSpot::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
    {
        lastPoint = event->pos();
        drawing = true;
    }
}

void InkSpot::mouseMoveEvent(QMouseEvent *event)
{
    if((event->buttons() & Qt::LeftButton) && drawing)
    {
        drawLineTo(event->pos());
    }
}

void InkSpot::mouseReleaseEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton && drawing)
    {
        drawLineTo(event->pos());
        drawing = false;
    }
}

void InkSpot::drawLineTo(const QPoint &endPoint)
{
    QPainter painter(&pixmap);
    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::NoBrush);

    QFile *stencilInput; // file for input, assumes a SQUARE RAW 8 bit grayscale image, no JPG no GIF, no size/format header, just 8 bit values in the file
    char *brushPrototype; // raw brush prototype
    uchar *brushData; // raw brush data

    stencilInput = new QFile("C:/brush3.raw");  // open raw file
    stencilInput->open(QIODevice::ReadOnly);
    QDataStream in;
    in.setDevice(stencilInput);
    int size = stencilInput->size();  // set size to the length of the raw file

    brushPrototype = new char[size];  // create the brush prototype array
    in.readRawData(brushPrototype, size);  // read the file into the prototype
    brushData = new uchar[size];  // create the uchar array you need to construct QImage

    for (int i = 0; i < size; ++i)
        brushData[i] = (uchar)brushPrototype[i];  // copy the char to the uchar array

    QImage test(brushData, 128, 128, QImage::Format_Indexed8); // create QImage from the brush data array
     // 128x128 was my raw file, for any file size just use the square root of the size variable provided it is SQUARE
    QImage test2(128, 128, QImage::Format_ARGB32);


   QVector<QRgb> vectorColors(256);  // create a color table for the image
    for (int c = 0; c < 256; c++)
        vectorColors[c] = qRgb(c, c, c);

    test.setColorTable(vectorColors);  // set the color table to the image

    for (int iX = 0; iX < 128; ++iX)  // fill all pixels with 255 0 0 (red) with random variations for OIL PAINT effect
    // use your color of choice and remove random stuff for solid color
    // the fourth parameter of setPixel is the ALPHA, use that to make your brush transparent by multiplying by opacity 0 to 1
    {
        for (int iY = 0; iY < 128; ++iY)
        {
            test2.setPixel(iX, iY, qRgba(255, 100, 100, (255-qGray(test.pixel(iX, iY)))*0.5));
        }
    }
    // final convertions of the stencil and color brush
    QPixmap testPixmap = QPixmap::fromImage(test2);
    QPixmap testPixmap2 = QPixmap::fromImage(test);

    painter.setBrush(Qt::NoBrush);
    painter.setPen(Qt::NoPen);
    // in a paint event you can test out both pixmaps
    QLineF line = QLineF(lastPoint, endPoint);
    float lineLength = line.length();
    qDebug() << line.length();
    line.setLength(lineLength / 50.0f);
    qDebug() << line.length();

    painter.drawPixmap(line.p1().x() - 16, line.p2().y() - 16, 32, 32, testPixmap);

    //delete all dynamically allocated objects with no parents
    delete [] brushPrototype;
    delete [] brushData;
    delete stencilInput;


    lastPoint = endPoint;

}


void InkSpot::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::NoBrush);
    QRect rect = event->rect();
    painter.drawPixmap(rect, pixmap, rect);
    update();

}

Answer 1

不要使用QLineF,使用QPainterPath- 它有一些非常方便的方法:

qreal QPainterPath::percentAtLength ( qreal len ) const
QPointF QPainterPath::pointAtPercent ( qreal t ) const
qreal length () const

因此,不是使用QLineF你创建一个只包含从旧图形光标位置到新图形光标位置的一条线的画家路径,获取该线条的长度,并迭代通过间距递增的长度以获得百分比值,你可以得到一个QPointF必须绘制画笔像素图的每个位置.就这么简单.

编辑:好的,这里是,没有测试过,大脑到终端,但是像这样:

QPointF lastPosition, currentPosition;
qreal spacing;

void draw() {
    QPainterPath path;
    path.moveTo(lastPosition);
    path.lineTo(currentPosition);
    qreal length = path.length();
    qreal pos = 0;

    while (pos < length) {
        qreal percent = path.percentAtLength(pos);
        drawYourPixmapAt(path.pointAtPercent(percent)); // pseudo method, use QPainter and your brush pixmap instead
        pos += spacing;
    }
}