I am trying to implement it with QQuickImageProvider but I am not understanding why it is not working. My code is below. If you could help me.

.h
Qt Code: 
  1. #ifndef MANIPULAIMAGEM_H
  2. #define MANIPULAIMAGEM_H
  3.  
  4. #include <QObject>
  5. #include <QImage>
  6. #include <QQuickImageProvider>
  7. #include <QQmlEngine>
  8. #include <QQmlContext>
  9.  
  10. class manipulaImagem : public QObject, public QQuickImageProvider
  11. {
  12.     Q_OBJECT
  13.  
  14. public slots:
  15.     QString recortarFotoPerfil(const QString &imagem, QRect rectRecorte);
  16.  
  17. public:
  18.     manipulaImagem(QObject *parent = 0);
  19.  
  20.     QImage requestImage(const QString &id, QSize *size, const QSize &requestedSize);
  21.  
  22. private:
  23.     void alocaImagem(const QString &imagem, QRect rectRecorte);
  24.  
  25.     QImage imagemEditada;
  26. };
  27.  
  28. #endif // MANIPULAIMAGEM_H
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.cpp
Qt Code: 
  1. #include "manipulaimagem.h"
  2.  
  3. #include <QDebug>
  4.  
  5. manipulaImagem::manipulaImagem(QObject *parent) : QQuickImageProvider(QQmlImageProviderBase::Image)
  6. {
  7.  
  8. }
  9.  
  10. QImage manipulaImagem::requestImage(const QString &id, QSize *size, const QSize &requestedSize)
  11. {
  12.     if(imagemEditada.isNull())
  13.     {
  14.         qDebug() << "Request image: (image is null)";
  15.     }
  16.     else
  17.     {
  18.         qDebug() << "Request image: image is OK";
  19.     }
  20.  
  21.     return imagemEditada;
  22. }
  23.  
  24. void manipulaImagem::alocaImagem(const QString &imagem, QRect rectRecorte)
  25. {
  26.     QUrl caminhoImagem(imagem);
  27.     QQmlEngine *engine = QQmlEngine::contextForObject(this)->engine();
  28.     QQmlImageProviderBase *imageProviderBase = engine->imageProvider(caminhoImagem.host());
  29.     QQuickImageProvider *imageProvider = static_cast<QQuickImageProvider*>(imageProviderBase);
  30.  
  31.     QSize imageSize;
  32.     QString imageId = caminhoImagem.path().remove(0, 1);
  33. imagemEditada = imageProvider->requestImage(imageId, &imageSize, imageSize);
  34.  
  35.     if(imagemEditada.isNull())
  36.     {
  37.         qDebug() << "Loading image failed";
  38.     }
  39.     else
  40.     {
  41.         qDebug() << "Loading image OK";
  42.     }
  43. }
  44.  
  45. QString manipulaImagem::recortarFotoPerfil(const QString &imagem, QRect rectRecorte)
  46. {
  47.     this->alocaImagem(imagem, rectRecorte);
  48.  
  49.     QString a = "image://ProvedorImagens/imagemEditada";
  50.  
  51.     if(imagemEditada.isNull())
  52.     {
  53.         qDebug() << "Imagem is null";
  54.     }
  55.     else
  56.     {
  57.         qDebug() << "Imagem is loaded";
  58.     }
  59.  
  60.     return a;
  61. }
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.qml
Qt Code: 
  1. ManipulaImagem {
  2.     id: manipulaImagem
  3. }
  4.  
  5. Camera {
  6.             id: camera
  7.  
  8.             captureMode: Camera.CaptureStillImage
  9.  
  10.             imageCapture {
  11.                 onImageCaptured: {
  12.                     previewImage.source = manipulaImagem.recortarFotoPerfil(preview, viewfinder.mapRectToSource(Qt.rect(viewfinder.x, viewfinder.y, viewfinder.width, viewfinder.height)));
  13.                 }
  14.             }
  15.         }
  16.  
  17. Rectangle {
  18.     id: previewRectangle
  19.  
  20.     visible: false
  21.  
  22.     anchors.fill: parent
  23.  
  24.     Image {
  25.         id: previewImage
  26.  
  27.         fillMode: Image.PreserveAspectFit
  28.  
  29.         anchors.top: parent.top
  30.  
  31.         width: parent.width
  32.         height: parent.width
  33.     }
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The output of this code is:

Loading image OK

Imagem is loaded

Request image: (image is null)

QML Image: Failed to get image from provider: image://provedorimagens/imagemEditada

What happens is that when I call the functions the image is not null, but when I try to return the QImage using the provider it cant return the image. I dont know why but for the image provider the image is null.

How could I solve that?