Get QVector<unsigned char> with all the data of an image

[JesusM]

How can I get a QVector<unsigned char> with all the data of a QImage?
I need to get all the unsigned char information of an image to use it as a texture in the GPU.

[jsulm]

@JesusM Why do you want to have the data in a QVector?! It would be quite inefficient.
There is https://doc.qt.io/qt-5/qimage.html#bits which you should use.
Even better is https://doc.qt.io/qt-5/qimage.html#constBits

[JesusM]

@jsulm
I need to translate this code to QT. This coe is done un MVS 2017 with c++ and I needed to use an external class to read the image

PagTexture::PagTexture(std::vector<std::string> rutas, std::vector<PagTexturesTypes> tipo)
{
	for (int i = 0; i < rutas.size(); i++)
	{
		std::string filename = rutas[i];
		PagTexturesTypes tipoTextura = tipo[i];
		/** Carga un png de disco https://lodev.org/lodepng/ */
		std::vector<unsigned char> image; // Los píxeles de la imagen
		unsigned width, height;
		unsigned error = lodepng::decode(image, width, height, filename);
		if (error)
		{
			std::cout << filename << " cannot be loaded" << std::endl;
			return;
		}
		// La textura se carga del revés, así que vamos a darle la vuelta
		unsigned char *imgPtr = &image[0];
		int numColorComponents = 4;
		int wInc = width * 4; //width in char
		unsigned char* top = nullptr;
		unsigned char* bot = nullptr;
		unsigned char temp = 0;
		for (int i = 0; i < height / 2; i++)
		{
			top = imgPtr + i * wInc;
			bot = imgPtr + (height - i - 1) * wInc;
			for (int j = 0; j < wInc; j++)
			{
				temp = *top;
				*top = *bot;
				*bot = temp;
				++top;
				++bot;
			}
		}

		//Construimos la textura con las imágenes que queremos y la función de cada imagen
	
				GLuint texture = 0;
				glGenTextures(1, &texture);
				glBindTexture(GL_TEXTURE_2D, texture);
				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
				glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height,0, GL_RGBA, GL_UNSIGNED_BYTE, image.data());
				glGenerateMipmap(GL_TEXTURE_2D);

				this->color = new PagImagen(image,width,height,texture);
				
               }
}
			

So I am using QImage but I don't know hoow to translate this lane .

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height,0, GL_RGBA, GL_UNSIGNED_BYTE, image.data());

What I've done by now is this. I used the .bit() you told me:

texture::texture(QVector<QString> rutas, QVector<TexturesTypes> tipo)
{
    for (int i = 0; i < rutas.size(); i++)
    {
        QString filename = rutas[i];
        TexturesTypes tipoTextura = tipo[i];

        QImage* imagen = new QImage(filename); // Los píxeles de la imagen
        int width, height;

        if (imagen == nullptr)
        {
            std::cout << filename.toStdString() << " cannot be loaded" << std::endl;
            return;
        }
        // La textura se carga del revés, así que vamos a darle la vuelta
        QImage imagenInvertida = imagen->rgbSwapped();
        width = imagenInvertida.width();
        height = imagenInvertida.height();
        
        //Construimos la textura con las imágenes que queremos y la función de cada imagen

                GLuint texture = 0;
                glGenTextures(1, &texture);
                glBindTexture(GL_TEXTURE_2D, texture);
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
                glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height,0, GL_RGBA, GL_UNSIGNED_BYTE, imagenInvertida.bits());
                //glGenerateMipmap(GL_TEXTURE_2D);

                this->color = new image(&imagenInvertida,width,height,texture);
              }
}
            

Is that rigth now? Is it tha same as I had before?.

[SGaist]

Hi,

It might be simpler to use a QOpenGLTexture.

[JesusM]

@SGaist so, if I use QOpenGLTextures, is it better to use QShaderProgram and QVertexArrayObjects instead of doing all the steps to get a GLuint id with the opengl functions?

[SGaist]

Depending on what where you would like to go with your application, you should consider studying modern OpenGL and go through the related Qt examples.

[JesusM]

@SGaist I am doing an OpenGL application to play with light settings in diferrent scenes woth different objects and materials

[SGaist]

Then I confirm my last suggestion.

[JesusM]

@SGaist ok, perfect so. Thanks a lot