按照我的最新问题：My OpenGL QQuickItem won't have the size I want，我现在正在尝试将其放入我的QQuickItem中，而不是为OpenGL视频设置一个任意大小。
我听说QQuickItem::transform()会给我一个变换矩阵的列表。我假设此列表包含达到我的QQuickItem的大小和位置的平方所需的所有转换。 <<<
既然如此，我就制作了以下最小的可验证和可编译示例，试图使绿屏适合我的QQuickItem的大小。但是目前，它只占用整个屏幕。
我使用了可以在下面找到的函数getModelMatrix()来获取所有转换并从中生成矩阵。然后我通过将这些转换应用于我的顶点着色器
gl_Position = u_transform * vertexIn;
正如我所说，结果是一个绿色屏幕。但是，它具有与我的窗口相同的尺寸，而不是
main.qml中指定的尺寸640x480和x，y = 0您可以在此处找到一个最小的可编译且可验证的示例：https://github.com/lucaszanella/openglqtquickexample/tree/88fe0092d663dd92c551c72acccd0bf058fe7e5b
OpenGlVideoQtQuick.cpp：
#include "OpenGlVideoQtQuick.h"
#define GET_STR(x) #x
#define A_VER 3
#define T_VER 4
//Simple shader. Outpus the same location as input, I guess
const char *vString2 = GET_STR(
attribute vec4 vertexIn;
attribute vec2 textureIn;
varying vec2 textureOut;
uniform mat4 u_transform;
void main(void)
{
gl_Position = u_transform * vertexIn;
textureOut = textureIn;
}
);
const char *tString2 = GET_STR(
varying vec2 textureOut;
uniform sampler2D tex_y;
uniform sampler2D tex_u;
uniform sampler2D tex_v;
void main(void)
{
vec3 yuv;
vec3 rgb;
yuv.x = texture2D(tex_y, textureOut).r;
yuv.y = texture2D(tex_u, textureOut).r - 0.5;
yuv.z = texture2D(tex_v, textureOut).r - 0.5;
rgb = mat3(1.0, 1.0, 1.0,
0.0, -0.39465, 2.03211,
1.13983, -0.58060, 0.0) * yuv;
gl_FragColor = vec4(rgb, 1.0);
}
);
OpenGlVideoQtQuick::OpenGlVideoQtQuick():
openGlVideoQtQuickRenderer(nullptr)
{
connect(this, &QQuickItem::windowChanged, this, &OpenGlVideoQtQuick::handleWindowChanged);
update();
}
void OpenGlVideoQtQuick::handleWindowChanged(QQuickWindow *win)
{
if (win) {
connect(win, &QQuickWindow::beforeSynchronizing, this, &OpenGlVideoQtQuick::sync, Qt::DirectConnection);
win->setClearBeforeRendering(false);
}
}
QMatrix4x4 OpenGlVideoQtQuick::getModelMatrix() {
QMatrix4x4 result;
// Compose model matrix from our transform properties in the QML
QQmlListProperty<QQuickTransform> transformations = transform();
const int count = transformations.count(&transformations);
for (int i=0; i<count; i++) {
QQuickTransform *transform = transformations.at(&transformations, i);
transform->applyTo(&result);
}
return result;
}
void OpenGlVideoQtQuick::update()
{
if (window())
window()->update();
}
OpenGlVideoQtQuickRenderer::~OpenGlVideoQtQuickRenderer()
{
delete program;
}
void OpenGlVideoQtQuick::sync()
{
if (!openGlVideoQtQuickRenderer) {
openGlVideoQtQuickRenderer = new OpenGlVideoQtQuickRenderer();
connect(window(), &QQuickWindow::beforeRendering, openGlVideoQtQuickRenderer, &OpenGlVideoQtQuickRenderer::render, Qt::DirectConnection);
connect(window(), &QQuickWindow::afterRendering, this, &OpenGlVideoQtQuick::update, Qt::DirectConnection);
}
this->openGlVideoQtQuickRenderer->qQuickVideoMatrix = getModelMatrix();
}
static const GLfloat ver[] = {
-1.0f,-1.0f,
1.0f,-1.0f,
-1.0f, 1.0f,
1.0f, 1.0f
};
static const GLfloat tex[] = {
0.0f, 1.0f,
1.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f
};
void OpenGlVideoQtQuickRenderer::render()
{
if (this->firstRun) {
std::cout << "Creating QOpenGLShaderProgram " << std::endl;
this->firstRun = false;
program = new QOpenGLShaderProgram();
initializeOpenGLFunctions();
std::cout << "Fragment Shader compilation: " << program->addShaderFromSourceCode(QOpenGLShader::Fragment, tString2) << std::endl;
std::cout << "Vertex Shader compilation: " << program->addShaderFromSourceCode(QOpenGLShader::Vertex, vString2) << std::endl;
program->bindAttributeLocation("vertexIn",A_VER);
program->bindAttributeLocation("textureIn",T_VER);
std::cout << "program->link() = " << program->link() << std::endl;
glGenTextures(3, texs);//TODO: ERASE THIS WITH glDeleteTextures
}
program->bind();
program->setUniformValue("u_transform", this->qQuickVideoMatrix);
//glViewport(50, 50, 50, 50);
glVertexAttribPointer(A_VER, 2, GL_FLOAT, 0, 0, ver);
glEnableVertexAttribArray(A_VER);
glVertexAttribPointer(T_VER, 2, GL_FLOAT, 0, 0, tex);
glEnableVertexAttribArray(T_VER);
unis[0] = program->uniformLocation("tex_y");
unis[1] = program->uniformLocation("tex_u");
unis[2] = program->uniformLocation("tex_v");
//Y
glBindTexture(GL_TEXTURE_2D, texs[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width, height, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
//U
glBindTexture(GL_TEXTURE_2D, texs[1]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width/2, height / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
//V
glBindTexture(GL_TEXTURE_2D, texs[2]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, width / 2, height / 2, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
glDrawArrays(GL_TRIANGLE_STRIP,0,4);
program->disableAttributeArray(A_VER);
program->disableAttributeArray(T_VER);
program->release();
}
OpenGlVideoQtQuick.h：
#ifndef OpenGlVideoQtQuick_H
#define OpenGlVideoQtQuick_H
#include <QtQuick/QQuickItem>
#include <QtGui/QOpenGLShaderProgram>
#include <QtGui/QOpenGLFunctions>
#include <QtQuick/qquickwindow.h>
#include <QtGui/QOpenGLShaderProgram>
#include <QtGui/QOpenGLContext>
#include <QString>
#include <iostream>
#include <QTimer>
class OpenGlVideoQtQuickRenderer : public QObject, protected QOpenGLFunctions
{
Q_OBJECT
public:
OpenGlVideoQtQuickRenderer() {
}
~OpenGlVideoQtQuickRenderer();
QMatrix4x4 qQuickVideoMatrix;
public slots:
void render();
private:
QOpenGLShaderProgram* program;
GLuint unis[3] = {0};
GLuint texs[3] = {0};
unsigned char *datas[3] = { 0 };
bool firstRun = true;
//TODO: make this variable according to video data
int width = 1920;
int height = 1080;
};
class OpenGlVideoQtQuick : public QQuickItem
{
Q_OBJECT
public:
OpenGlVideoQtQuick();
QMatrix4x4 getModelMatrix();
private slots:
void handleWindowChanged(QQuickWindow *win);
public slots:
void sync();
void update();//Updates the window
private:
OpenGlVideoQtQuickRenderer *openGlVideoQtQuickRenderer;
};
#endif // OpenGlVideoQtQuick_H
main.qml：
import QtQuick 2.0
import OpenGLComponents 1.0
Item {
width: 1280
height: 720
OpenGlVideoQtQuick {
width: 640
height: 480
}
}
最佳答案
从您的问题和代码中，您并不清楚要“看到”什么，但是我确实看到了一些可能对您有所帮助的问题：
我认为您的渲染循环实际上没有被调用。您必须在构造函数中执行此操作：setFlag(ItemHasContents);
确保您确实将一些纹理/视频数据传递到您的glTexImage2D()调用中，否则会得到一些垃圾（随机的绿色垃圾？）
您可能想看看QQuickItem::widthChanged和QQuickItem::heightChanged信号
确保在调试时具有glViewport()和glClear()调用，以避免混淆-您可以稍后在不再需要它们时将其删除
关于c++ - 如何使OpenGL视频具有与QQuickItem相同的大小和位置？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/54902244/