Q_GUI_EXPORT QImage qt_gl_read_framebuffer(const QSize &size, bool alpha_format, bool include_alpha)
{
    int w = size.width();
    int h = size.height();

    QOpenGLFunctions *funcs = QOpenGLContext::currentContext()->functions();
    while (funcs->glGetError());

#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
    QImage img(size, (alpha_format && include_alpha) ? QImage::Format_ARGB32_Premultiplied
                                                     : QImage::Format_RGB32);
#ifdef QT_OPENGL_ES
    GLint fmt = GL_BGRA_EXT;
#else
    GLint fmt = GL_BGRA;
#endif
    funcs->glReadPixels(0, 0, w, h, fmt, GL_UNSIGNED_BYTE, img.bits());
    if (!funcs->glGetError())
        return img.mirrored();
#endif

    QImage rgbaImage(size, (alpha_format && include_alpha) ? QImage::Format_RGBA8888_Premultiplied
                                                           : QImage::Format_RGBX8888);
    funcs->glReadPixels(0, 0, w, h, GL_RGBA, GL_UNSIGNED_BYTE, rgbaImage.bits());
    return rgbaImage.mirrored();
}
Пример #2
0
void QSGDistanceFieldGlyphCache::saveTexture(GLuint textureId, int width, int height) const
{
    QOpenGLFunctions *functions = QOpenGLContext::currentContext()->functions();

    GLuint fboId;
    functions->glGenFramebuffers(1, &fboId);

    GLuint tmpTexture = 0;
    functions->glGenTextures(1, &tmpTexture);
    functions->glBindTexture(GL_TEXTURE_2D, tmpTexture);
    functions->glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
    functions->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    functions->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    functions->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    functions->glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    functions->glBindTexture(GL_TEXTURE_2D, 0);

    functions->glBindFramebuffer(GL_FRAMEBUFFER_EXT, fboId);
    functions->glFramebufferTexture2D(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D,
                                      tmpTexture, 0);

    functions->glActiveTexture(GL_TEXTURE0);
    functions->glBindTexture(GL_TEXTURE_2D, textureId);

    functions->glDisable(GL_STENCIL_TEST);
    functions->glDisable(GL_DEPTH_TEST);
    functions->glDisable(GL_SCISSOR_TEST);
    functions->glDisable(GL_BLEND);

    GLfloat textureCoordinateArray[8];
    textureCoordinateArray[0] = 0.0f;
    textureCoordinateArray[1] = 0.0f;
    textureCoordinateArray[2] = 1.0f;
    textureCoordinateArray[3] = 0.0f;
    textureCoordinateArray[4] = 1.0f;
    textureCoordinateArray[5] = 1.0f;
    textureCoordinateArray[6] = 0.0f;
    textureCoordinateArray[7] = 1.0f;

    GLfloat vertexCoordinateArray[8];
    vertexCoordinateArray[0] = -1.0f;
    vertexCoordinateArray[1] = -1.0f;
    vertexCoordinateArray[2] =  1.0f;
    vertexCoordinateArray[3] = -1.0f;
    vertexCoordinateArray[4] =  1.0f;
    vertexCoordinateArray[5] =  1.0f;
    vertexCoordinateArray[6] = -1.0f;
    vertexCoordinateArray[7] =  1.0f;

    functions->glViewport(0, 0, width, height);
    functions->glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vertexCoordinateArray);
    functions->glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, textureCoordinateArray);

    {
        static const char *vertexShaderSource =
                "attribute vec4      vertexCoordsArray; \n"
                "attribute vec2      textureCoordArray; \n"
                "varying   vec2      textureCoords;     \n"
                "void main(void) \n"
                "{ \n"
                "    gl_Position = vertexCoordsArray;   \n"
                "    textureCoords = textureCoordArray; \n"
                "} \n";

        static const char *fragmentShaderSource =
                "varying   vec2      textureCoords; \n"
                "uniform   sampler2D         texture;       \n"
                "void main() \n"
                "{ \n"
                "    gl_FragColor = texture2D(texture, textureCoords); \n"
                "} \n";

        GLuint vertexShader = functions->glCreateShader(GL_VERTEX_SHADER);
        GLuint fragmentShader = functions->glCreateShader(GL_FRAGMENT_SHADER);

        if (vertexShader == 0 || fragmentShader == 0) {
            GLenum error = functions->glGetError();
            qWarning("QSGDistanceFieldGlyphCache::saveTexture: Failed to create shaders. (GL error: %x)",
                     error);
            return;
        }

        functions->glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
        functions->glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
        functions->glCompileShader(vertexShader);

        GLint len = 1;
        functions->glGetShaderiv(vertexShader, GL_INFO_LOG_LENGTH, &len);

        char infoLog[2048];
        functions->glGetShaderInfoLog(vertexShader, 2048, NULL, infoLog);
        if (qstrlen(infoLog) > 0)
            qWarning("Problems compiling vertex shader:\n %s", infoLog);

        functions->glCompileShader(fragmentShader);
        functions->glGetShaderInfoLog(fragmentShader, 2048, NULL, infoLog);
        if (qstrlen(infoLog) > 0)
            qWarning("Problems compiling fragment shader:\n %s", infoLog);

        GLuint shaderProgram = functions->glCreateProgram();
        functions->glAttachShader(shaderProgram, vertexShader);
        functions->glAttachShader(shaderProgram, fragmentShader);

        functions->glBindAttribLocation(shaderProgram, 0, "vertexCoordsArray");
        functions->glBindAttribLocation(shaderProgram, 1, "textureCoordArray");

        functions->glLinkProgram(shaderProgram);
        functions->glGetProgramInfoLog(shaderProgram, 2048, NULL, infoLog);
        if (qstrlen(infoLog) > 0)
            qWarning("Problems linking shaders:\n %s", infoLog);

        functions->glUseProgram(shaderProgram);
        functions->glEnableVertexAttribArray(0);
        functions->glEnableVertexAttribArray(1);

        int textureUniformLocation = functions->glGetUniformLocation(shaderProgram, "texture");
        functions->glUniform1i(textureUniformLocation, 0);
    }

    functions->glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

    {
        GLenum error = functions->glGetError();
        if (error != GL_NO_ERROR)
            qWarning("glDrawArrays reported error 0x%x", error);
    }

    uchar *data = new uchar[width * height * 4];

    functions->glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);

    QImage image(data, width, height, QImage::Format_ARGB32);

    QByteArray fileName = m_referenceFont.familyName().toLatin1() + '_' + QByteArray::number(textureId);
    fileName = fileName.replace('/', '_').replace(' ', '_') + ".png";

    image.save(QString::fromLocal8Bit(fileName));

    {
        GLenum error = functions->glGetError();
        if (error != GL_NO_ERROR)
            qWarning("glReadPixels reported error 0x%x", error);
    }

    functions->glDisableVertexAttribArray(0);
    functions->glDisableVertexAttribArray(1);

    functions->glDeleteFramebuffers(1, &fboId);
    functions->glDeleteTextures(1, &tmpTexture);

    delete[] data;
}