qt opengl 离线渲染，为啥在windows下正常， ios下image为空白？

蜗牛的信仰 2015-07-22 03:09:35

请问一下， qt opengl 离线渲染，为啥在windows下正常， ios下image为空白？



#include <QtCore>

#include <QtGui>

#include <QtWidgets>



void nativePainting()

{

    static const float vertexPositions[] = {

        -0.8f, -0.8f, 0.0f,

         0.8f, -0.8f, 0.0f,

         0.0f,  0.8f, 0.0f

    };



    static const float vertexColors[] = {

        1.0f, 0.0f, 0.0f,

        0.0f, 1.0f, 0.0f,

        0.0f, 0.0f, 1.0f

    };



    QOpenGLBuffer vertexPositionBuffer(QOpenGLBuffer::VertexBuffer);

    vertexPositionBuffer.create();

    vertexPositionBuffer.setUsagePattern(QOpenGLBuffer::StaticDraw);

    vertexPositionBuffer.bind();

    vertexPositionBuffer.allocate(vertexPositions, 9 * sizeof(float));



    QOpenGLBuffer vertexColorBuffer(QOpenGLBuffer::VertexBuffer);

    vertexColorBuffer.create();

    vertexColorBuffer.setUsagePattern(QOpenGLBuffer::StaticDraw);

    vertexColorBuffer.bind();

    vertexColorBuffer.allocate(vertexColors, 9 * sizeof(float));



    QOpenGLShaderProgram program;

    program.addShaderFromSourceCode(QOpenGLShader::Vertex,

                                    "#version 330\n"

                                    "in vec3 position;\n"

                                    "in vec3 color;\n"

                                    "out vec3 fragColor;\n"

                                    "void main() {\n"

                                    "    fragColor = color;\n"

                                    "    gl_Position = vec4(position, 1.0);\n"

                                    "}\n"

                                    );

    program.addShaderFromSourceCode(QOpenGLShader::Fragment,

                                    "#version 330\n"

                                    "in vec3 fragColor;\n"

                                    "out vec4 color;\n"

                                    "void main() {\n"

                                    "    color = vec4(fragColor, 1.0);\n"

                                    "}\n"

                                    );

    program.link();

    program.bind();



    vertexPositionBuffer.bind();

    program.enableAttributeArray("position");

    program.setAttributeBuffer("position", GL_FLOAT, 0, 3);



    vertexColorBuffer.bind();

    program.enableAttributeArray("color");

    program.setAttributeBuffer("color", GL_FLOAT, 0, 3);



    glDrawArrays(GL_TRIANGLES, 0, 3);

}



QImage createImageWithFBO()

{

    QSurfaceFormat format;

    // format.setMajorVersion(3); ios 下注释

   // format.setMinorVersion(3); iOS 下注释



    QWindow window;

    window.setSurfaceType(QWindow::OpenGLSurface);

    window.setFormat(format);

    window.create();



    QOpenGLContext context;

    context.setFormat(format);

    if (!context.create())

        qFatal("Cannot create the requested OpenGL context!");

    context.makeCurrent(&window);



    const QRect drawRect(0, 0, 400, 400);

    const QSize drawRectSize = drawRect.size();



    QOpenGLFramebufferObjectFormat fboFormat;

    fboFormat.setSamples(16);

    fboFormat.setAttachment(QOpenGLFramebufferObject::CombinedDepthStencil);



    QOpenGLFramebufferObject fbo(drawRectSize, fboFormat);

    fbo.bind();



    QOpenGLPaintDevice device(drawRectSize);

    QPainter painter;

    painter.begin(&device);

    painter.setRenderHints(QPainter::Antialiasing | QPainter::HighQualityAntialiasing);



    painter.fillRect(drawRect, Qt::blue);



    painter.drawTiledPixmap(drawRect, QPixmap(":/qt-project.org/qmessagebox/images/qtlogo-64.png"));



    painter.setPen(QPen(Qt::green, 5));

    painter.setBrush(Qt::red);

    painter.drawEllipse(0, 100, 400, 200);

    painter.drawEllipse(100, 0, 200, 400);



    painter.beginNativePainting();

    nativePainting();

    painter.endNativePainting();



    painter.setPen(QPen(Qt::white, 0));

    QFont font;

    font.setPointSize(24);

    painter.setFont(font);

    painter.drawText(drawRect, "Hello FBO", QTextOption(Qt::AlignCenter));



    painter.end();



    fbo.release();

    return fbo.toImage();

}



int main(int argc, char **argv)

{

    QApplication app(argc, argv);



    QImage targetImage = createImageWithFBO();



    QLabel label;

    label.setPixmap(QPixmap::fromImage(targetImage));

    label.show();

    return app.exec();

}