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I have copied the QImage into OpenGL Texture below. If I want to render the Texture, should I
just bind the Texture in Flush() ? Or should I have to do anything else? Please find my below
code
void SaveBackBuffer() {
QPixmap pixmap = QPixmap::grabWindow(this->winId());
QImage buf = pixmap.toImage();
_savedBackBuffer = buf.convertToFormat(QImage::Format_RGBA8888);
}
void RestoreBackBuffer() {
glBindTexture(GL_TEXTURE_2D, _scrTex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, _savedBackBuffer.width(),
_savedBackBuffer.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE,
_savedBackBuffer.bits());
glBindTexture(GL_TEXTURE_2D, 0);
_bSavingBackBuffer = false;
}
Flush() {
glBindTexture(GL_TEXTURE_2D, _scrTex);
...
glDrawArrays...
}
I attached 4 color buffers to a framebuffer and render in each of them. Each color buffer has the size of the window. I'm trying to read the color of the pixels of one of these color buffers using the coordinates of the mouse pointer.
mouse move event handler
void mouseMoveEvent(QMouseEvent *event)
{
int x = event->pos().x();
int y = event->pos().y();
makeCurrent();
glBindFramebuffer(GL_READ_FRAMEBUFFER, FBOIndex::GEOMETRY);
{
// I save the values I'm interested in in the attachment GL_COLOR_ATTACHMENT3
// but I always get 0 from any other attachment I try
glReadBuffer(GL_COLOR_ATTACHMENT3);
QVector<GLubyte> pixel(3);
glReadPixels(x, geometry().height() - y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &(pixel[0]));
QString PixelColor = QColor(pixel[0], pixel[1], pixel[2]).name();
qDebug() << PixelColor; // => always 0
}
glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebufferObject());
doneCurrent();
}
But for every color buffer I always read the value 0.
The color buffers are written correctly during the rendering phase, I tested each of them by displaying the texture to which they are attached. I also tested the pixel-reading selected by the mouse pointer to the default framebuffer and it works correctly.
Where am I wrong?
Thanks!
EDIT
The seemingly strange thing is that, if I use a "dedicated" framebuffer, I can correctly read the values stored in the texture.
void mouseMoveEvent(QMouseEvent *event)
{
int x = event->pos().x();
int y = event->pos().y();
GLuint fbo;
makeCurrent();
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
{
GLuint texture = textures[TextureIndex::COLOUR];
glBindTexture(GL_TEXTURE_2D, texture);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);
QVector<GLubyte> pixel(3);
glReadPixels(x, geometry().height() - y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &(pixel[0]));
QString PixelColor = QColor(pixel[0], pixel[1], pixel[2]).name();
qDebug() << PixelColor; // => correct value
}
glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebufferObject());
glDeleteFramebuffers(1, &fbo);
doneCurrent();
}
But clearly it seems useless to use another framebuffer when I already have one with exactly the information I need.
I also tried to read directly the values of the texture (as suggested by #Spektre), but also in this case I always get 0.
void mouseMoveEvent(QMouseEvent *event)
{
int x = event->pos().x();
int y = event->pos().y();
makeCurrent();
{
GLuint texture = textures[TextureIndex::COLOUR];
glBindTexture(GL_TEXTURE_2D, texture);
glTexSubImage2D(GL_TEXTURE_2D, 0, x, geometry().height() - y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &(pixel[0]));
QString PixelColor = QColor(pixel[0], pixel[1], pixel[2]).name();
qDebug() << PixelColor; // => always 0
}
doneCurrent();
}
My approach is correct, but I was not binding to the correct framebuffer.
FBOIndex::GEOMETRY is an enum value that I use to index a FBOs array, where I store all the framebuffer object names, so in general it is not a correct framebuffer object name.
I have defined a method addFBO(index) that creates a framebuffer and stores it at the position index in the FBOs array. The method returns the framebuffer object name of the generated framebuffer. If a framebuffer already exists at the position index, then the method simply returns the associated framebuffer object name.
So, by changing the code in the following way, I finally get the desired result.
void mouseMoveEvent(QMouseEvent *event)
{
int x = event->pos().x();
int y = event->pos().y();
makeCurrent();
glBindFramebuffer(GL_READ_FRAMEBUFFER, addFBO(FBOIndex::GEOMETRY));
{
glReadBuffer(GL_COLOR_ATTACHMENT3);
QVector<GLubyte> pixel(3);
glReadPixels(x, geometry().height() - y, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &(pixel[0]));
QString PixelColor = QColor(pixel[0], pixel[1], pixel[2]).name();
qDebug() << PixelColor; // => correct value
}
glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebufferObject());
doneCurrent();
}
I would like to show a color image from the kinect v2 sensor over openGl in a Qt widget. The problem is, that the presentation of this image is incorrect.
Here is the code where I get the color frame:
class:
cv::Mat ColorMap;
std::vector<BYTE> colorBuffer;
int color_width;
int color_height;
code:
if(colorBuffer.empty())
colorBuffer.resize(color_height * color_width * 4 * sizeof(unsigned char));
hr = ColorFrame->CopyConvertedFrameDataToArray((UINT)colorBuffer.size(),
&colorBuffer[0], ColorImageFormat::ColorImageFormat_Bgra );
ColorMap = cv::Mat( color_height, color_width, CV_8UC4, &colorBuffer[0]);
That means, I get the color information as BGR Format with an alpha channel and copy it to a matrix with 4 channels, (BRGA) and each channel has 8Bit from 0 to 255. Correct?
In the next step, I resize it as the same size as the widget:
Kinect->CreateFrame();
cv::Mat GUIColorImage;
Kinect->ColorMap.copyTo(GUIColorImage);
cv::resize(GUIColorImage,GUIColorImage,
cv::Size(ui->Left_Widget_Color->width(),ui->Left_Widget_Color->height()));
Than I've tried two convert methods:
1. convert to BGR
2. convert to 8UC3 (8-Bit, unsigned char, 3 channels (the same as BGR?))
1: GUIColorImage.convertTo(GUIColorImage,CV_BGRA2BGR);
2: GUIColorImage.convertTo(GUIColorImage,CV_8UC3);
But no solutions works.
After the conversion, I try to display it over openGl with:
LeftWidgetColor.UpdateImage(GUIColorImage);
LeftWidgetColor is a QOpenGLWidget:
header:
class RenderWidget : public QOpenGLWidget
{
Q_OBJECT
public:
RenderWidget(QWidget *parent);
~RenderWidget();
void UpdateImage(cv::Mat newimage);
void initializeGL();
void paintGL();
private:
int width;
int height;
GLuint texture;
cv::Mat image;
signals:
void info(QString msg);
void error(QString msg);
void DepthValueAt(cv::Point2i DepthPosition);
protected:
void mousePressEvent(QMouseEvent *event);
void mouseReleaseEvent(QMouseEvent *event);
void mouseMoveEvent(QMouseEvent *event);
};
code:
RenderWidget::RenderWidget(QWidget *parent) : QOpenGLWidget(parent)
{
width = this->size().width();
height = this->size().height();
texture = 0;
initializeGL();
}
RenderWidget::~RenderWidget()
{
glDeleteTextures(1, &texture);
}
void RenderWidget::initializeGL()
{
//Background Color is black
glClearColor(0,0,0,1);
//Storage of Pixelmode for two-dimensional textures
glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
//Create texture
glGenTextures(1, &texture);
glViewport(0, 0, width, height);
}
void RenderWidget::paintGL()
{
// Clear the screen and depth buffer (with black)
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Select the model view matrix and reset it
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0.0f, 0.0f, 0.0f);
// Abort drawing if OpenCV was unable to open the camera
if (image.empty())
{
return;
}
glEnable(GL_TEXTURE_RECTANGLE_ARB);
// Typical texture generation using data from the bitmap
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texture);
// Transfer image data to the GPU
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
3, image.cols, image.rows, 0,
GL_BGR, GL_UNSIGNED_BYTE, image.data);
if (glGetError() != GL_NO_ERROR)
{
}
// Draw a 2D face with texture
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex2f(1, 1);
glTexCoord2f(image.cols, 0); glVertex2f(-1, 1);
glTexCoord2f(image.cols, image.rows); glVertex2f(-1, -1);
glTexCoord2f(0, image.rows); glVertex2f(1, -1);
glEnd();
glDisable(GL_TEXTURE_RECTANGLE_ARB);
}
void RenderWidget::UpdateImage(cv::Mat newimage)
{
newimage.copyTo(image);
update();
}
I guess the problem is in:
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
3, image.cols, image.rows, 0,
GL_BGR, GL_UNSIGNED_BYTE, image.data);
But I can't find it. I've declared 3-channels, BGR, 8-Bit = 1 Byte as unsigned. Does someone know where the mistake is?
If i show it over imshow (openCv class), it works fine.
My Mistake was, that I used cv::Mat::convertTo(): but here
they wrote, that convertTo() should not used to convert the format (Only to change the data type). cv::cvtColor is the right function and it works well for me. So I've changed the conversion from:
GUIColorImage.convertTo(GUIColorImage,CV_BGRA2BGR);
to
cv::cvtColor(GUIColorImage,GUIColorImage,CV_BGRA2BGR);
My program displays video frames as OpenGL textures.
I have problems with OpenGL initialization. To see video I need to start rendering thread, stop it and start again. I think I am missing something in CRenderThread::InitOpenGL() function. What should I do for correct OpenGL initialization?
My environment:
Windows 7 x64
Microsoft Visual Studio 2008 x64
Here is the code:
#include "RenderThread.h"
#include <QtDebug>
#include <vm_time.h>
static Ipp32u UMCToInternalFormat(UMC::ColorFormat format)
{
switch(format)
{
case UMC::BGR24: return GL_BGR;
case UMC::BGR32: return GL_BGRA;
case UMC::RGB24: return GL_RGB;
case UMC::RGB32: return GL_RGBA;
}
return 0;
}
CRenderThread::CRenderThread(const WId& rnWindowHandle)
: m_bInitialized(false)
, m_WindowHandle(rnWindowHandle)
, m_Texture(0)
, m_fTextureWidth(0.0f)
, m_fTextureHeight(0.0f)
, m_nFrameWidth(0)
, m_nFrameHeight(0)
, m_nWindowWidth(0)
, m_nWindowHeight(0)
{
}
void CRenderThread::PrepareWork()
{
// Wait until first frame comes
if(!m_bAbort)
Suspend();
}
void CRenderThread::DoOnStop()
{
if(m_WindowGLResourceContext)
{
wglDeleteContext(m_WindowGLResourceContext);
m_WindowGLResourceContext = 0;
}
ReleaseDC(m_WindowHandle, m_WindowDC);
if(m_Texture)
{
glDeleteTextures(1, &m_Texture);
m_Texture = 0;
}
}
void CRenderThread::InitOpenGL()
{
PIXELFORMATDESCRIPTOR pfd = {
sizeof(PIXELFORMATDESCRIPTOR), 1, PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 16, 0, 0, PFD_MAIN_PLANE, 0, 0, 0, 0
};
m_WindowDC = GetDC(m_WindowHandle);
if(!m_WindowDC)
return;
if(!SetPixelFormat(m_WindowDC, ChoosePixelFormat(m_WindowDC, &pfd), &pfd))
return;
m_WindowGLResourceContext = wglCreateContext(m_WindowDC); // create rendering context
if(!m_WindowGLResourceContext)
return;
if(!wglMakeCurrent(m_WindowDC, m_WindowGLResourceContext)) // set it as current
return;
// OpenGL context already tied to output window
// to disable all slow GL components
// it is not mandatory to disable all if we have accelerated card
glClearColor(0.0f, 170.0f, 255.0f, 1.0f);
glClearDepth(1.0);
glDepthFunc(GL_NEVER);
// disable slow GL extensions
glDisable(GL_DEPTH_TEST); glDisable(GL_ALPHA_TEST); glDisable(GL_BLEND);
glDisable(GL_DITHER); glDisable(GL_FOG); glDisable(GL_STENCIL_TEST);
glDisable(GL_LIGHTING); glDisable(GL_LOGIC_OP); glDisable(GL_TEXTURE_1D);
glDisable(GL_TEXTURE_2D);
glPixelTransferi(GL_MAP_COLOR, GL_FALSE);
glPixelTransferi(GL_RED_SCALE, 1); glPixelTransferi(GL_RED_BIAS, 0);
glPixelTransferi(GL_GREEN_SCALE, 1); glPixelTransferi(GL_GREEN_BIAS, 0);
glPixelTransferi(GL_BLUE_SCALE, 1); glPixelTransferi(GL_BLUE_BIAS, 0);
glPixelTransferi(GL_ALPHA_SCALE, 1); glPixelTransferi(GL_ALPHA_BIAS, 0);
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &m_Texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glViewport(0, 0, m_nWindowWidth, m_nWindowHeight);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glRasterPos2i(-1, 1); // move to the upper left corner
glPixelZoom(1.0, -1.0); // top to bottom
SwapBuffers(m_WindowDC);
m_bInitialized = true;
}
void CRenderThread::SetRenderFrame(PVideoData pFrame)
{
Q_ASSERT(pFrame.get());
{
//boost::mutex::scoped_lock Lock(m_FrameMutex);
m_pFrameToRender = pFrame;
}
// Resume thread to render current frame
Resume();
}
void CRenderThread::DoWork()
{
IppiSize CurWinSize;
UMC::Status nStatus = UMC::UMC_OK;
::RECT rect;
GetClientRect(m_WindowHandle, &rect);
CurWinSize.height = rect.bottom;
CurWinSize.width = rect.right;
if(!m_bInitialized)
InitOpenGL();
if(CurWinSize.width > IPP_MAX_16S || CurWinSize.height > IPP_MAX_16S) // window seems to be destroyed
return;
// reinit buffers if window size has been changed
if(CurWinSize.height != m_nWindowHeight || CurWinSize.width != m_nWindowWidth)
{
m_nWindowWidth = CurWinSize.width;
m_nWindowHeight = CurWinSize.height;
glViewport(0, 0, m_nWindowWidth, m_nWindowHeight);
}
// Render frame
{
//boost::mutex::scoped_lock Lock(m_FrameMutex);
if(m_pFrameToRender.get())
{
if(m_nWindowWidth && m_nWindowHeight)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
m_nFrameWidth = m_pFrameToRender->GetWidth();
m_nFrameHeight = m_pFrameToRender->GetHeight();
m_nRenderFormat = UMCToInternalFormat(m_pFrameToRender->GetColorFormat());
glTexImage2D(GL_TEXTURE_2D, 0, 3, m_nFrameWidth, m_nFrameHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, m_pFrameToRender->GetBufferPointer());
//glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, m_nFrameWidth, m_nFrameHeight, m_nRenderFormat, GL_UNSIGNED_BYTE, m_pFrameToRender->GetBufferPointer());
glBegin(GL_POLYGON);
glTexCoord2i(0, 0); glVertex2f(-1.0, 1.0);
glTexCoord2i(1, 0); glVertex2f( 1.0, 1.0);
glTexCoord2i(1, 1); glVertex2f( 1.0, -1.0);
glTexCoord2i(0, 1); glVertex2f(-1.0, -1.0);
glEnd();
glFlush();
SwapBuffers(m_WindowDC); // to draw on physical screen
}
}
}
// Wait for next frame to render
if(!m_bAbort)
Suspend();
}
Couple thoughts, not all necessarily related to your problem:
glClearColor(0.0f, 170.0f, 255.0f, 1.0f);
Clear color is clamped to the range of [0,1], not [0,255].
// disable slow GL extensions
glDisable(GL_DEPTH_TEST); glDisable(GL_ALPHA_TEST); glDisable(GL_BLEND);
glDisable(GL_DITHER); glDisable(GL_FOG); glDisable(GL_STENCIL_TEST);
glDisable(GL_LIGHTING); glDisable(GL_LOGIC_OP); glDisable(GL_TEXTURE_1D);
glDisable(GL_TEXTURE_2D);
These (and most all opengl settings) are disabled by default. These are all doing nothing. Not hurting anything though.
glPixelTransferi(GL_MAP_COLOR, GL_FALSE);
glPixelTransferi(GL_RED_SCALE, 1); glPixelTransferi(GL_RED_BIAS, 0);
glPixelTransferi(GL_GREEN_SCALE, 1); glPixelTransferi(GL_GREEN_BIAS, 0);
glPixelTransferi(GL_BLUE_SCALE, 1); glPixelTransferi(GL_BLUE_BIAS, 0);
glPixelTransferi(GL_ALPHA_SCALE, 1); glPixelTransferi(GL_ALPHA_BIAS, 0);
Again, these are all the defaults.
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &m_Texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
This might actually be a real problem. glTexParameter only effects the currently bound texture, but you're calling them here with no texture bound. So these are doing nothing. When you actually do use a texture later, it will have mipmapping set on the min filter, which could cause it not to be displayed. Move your glTexParameter calls to after you have bound the texture that you want them to effect.
I've been attempting to render text onto an openGL window using SDL and the SDL_TTF library on windows XP, VS2010.
Versions:
SDL version 1.2.14
SDL TTF devel 1.2.10
openGL (version is at least 2-3 years old).
I have successfully created an openGL window using SDL / SDL_image and can render lines / polygons onto it with no problems.
However, moving onto text it appears that there is some flaw in my current program, I am getting the following result when trying this code here
for those not willing to pastebin here are only the crutial code segments:
void drawText(char * text) {
glLoadIdentity();
SDL_Color clrFg = {0,0,255,0}; // set colour to blue (or 'red' for BGRA)
SDL_Surface *sText = TTF_RenderUTF8_Blended( fntCourier, text, clrFg );
GLuint * texture = create_texture(sText);
glBindTexture(GL_TEXTURE_2D, *texture);
// draw a polygon and map the texture to it, may be the source of error
glBegin(GL_QUADS); {
glTexCoord2i(0, 0); glVertex3f(0, 0, 0);
glTexCoord2i(1, 0); glVertex3f(0 + sText->w, 0, 0);
glTexCoord2i(1, 1); glVertex3f(0 + sText->w, 0 + sText->h, 0);
glTexCoord2i(0, 1); glVertex3f(0, 0 + sText->h, 0);
} glEnd();
// free the surface and texture, removing this code has no effect
SDL_FreeSurface( sText );
glDeleteTextures( 1, texture );
}
segment 2:
// create GLTexture out of SDL_Surface
GLuint * create_texture(SDL_Surface *surface) {
GLuint texture = 0;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
// The SDL_Surface appears to have BGR_A formatting, however this ends up with a
// white rectangle no matter which colour i set in the previous code.
int Mode = GL_RGB;
if(surface->format->BytesPerPixel == 4) {
Mode = GL_RGBA;
}
glTexImage2D(GL_TEXTURE_2D, 0, Mode, surface->w, surface->h, 0, Mode,
GL_UNSIGNED_BYTE, surface->pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
return &texture;
}
Is there an obvious bit of code I am missing?
Thank you for any help on this subject.
I've been trying to learn openGL and SDL for 3 days now, so please forgive any misinformation on my part.
EDIT:
I notice that using
TTF_RenderUTF8_Shaded
TTF_RenderUTF8_Solid
Throw a null pointer exception, meaning that there is an error within the actual text rendering function (I suspect), I do not know how this means TTF_RenderUTF8_Blended returns a red square but I suspect all troubles hinge on this.
I think the problem is in the glEnable(GL_TEXTURE_2D) and glDisable(GL_TEXTURE_2D) functions which must be called every time the text is painted on the screen.And maybe also the color conversion between the SDL and GL surface is not right.
I have combined create_texture and drawText into a single function that displays the text properly. That's the code:
void drawText(char * text, TTF_Font* tmpfont) {
SDL_Rect area;
SDL_Color clrFg = {0,0,255,0};
SDL_Surface *sText = SDL_DisplayFormatAlpha(TTF_RenderUTF8_Blended( tmpfont, text, clrFg ));
area.x = 0;area.y = 0;area.w = sText->w;area.h = sText->h;
SDL_Surface* temp = SDL_CreateRGBSurface(SDL_HWSURFACE|SDL_SRCALPHA,sText->w,sText->h,32,0x000000ff,0x0000ff00,0x00ff0000,0x000000ff);
SDL_BlitSurface(sText, &area, temp, NULL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, sText->w, sText->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, temp->pixels);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS); {
glTexCoord2d(0, 0); glVertex3f(0, 0, 0);
glTexCoord2d(1, 0); glVertex3f(0 + sText->w, 0, 0);
glTexCoord2d(1, 1); glVertex3f(0 + sText->w, 0 + sText->h, 0);
glTexCoord2d(0, 1); glVertex3f(0, 0 + sText->h, 0);
} glEnd();
glDisable(GL_TEXTURE_2D);
SDL_FreeSurface( sText );
SDL_FreeSurface( temp );
}
screenshot
I'm initializing OpenGL as follows:
int Init(){
glClearColor( 0.1, 0.2, 0.2, 1);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho( 0, 600, 300, 0, -1, 1 );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
if( glGetError() != GL_NO_ERROR ){
return false;
}
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
}
I think you should just add glEnable(GL_BLEND), because the code for the text surface says TTF_RenderUTF8_Blended( fntCourier, text, clrFg ) and you have to enable the blending abilities of opengl.
EDIT
Okay, I finally took the time to put your code through a compiler. Most importantly, compiler with -Werror so that warning turn into errors
GLuint * create_texture(SDL_Surface *surface) {
GLuint texture = 0;
/*...*/
return &texture;
}
I didn't see it first, because that's something like C coder's 101 and is quite unexpected: You must not return pointers to local variables!. Once the functions goes out of scope the pointer returned will point to nonsense only. Why do you return a pointer at all? Just return a integer:
GLuint create_texture(SDL_Surface *surface) {
GLuint texture = 0;
/*...*/
return texture;
}
Because of this you're also not going to delete the texture afterward. You upload it to OpenGL, but then loose the reference to it.
Your code misses a glEnable(GL_TEXTURE_2D) that's why you can't see any effects of texture. However your use of textures is suboptimal. They way you did it, you recreate a whole new texture each time you're about to draw that text. If that happens in a animation loop, you'll
run out of texture memory rather soon
slow it down significantly
(1) can be addressed by not generating a new texture name each redraw
(2) can be addresses by uploading new texture data only when the text changes and by not using glTexImage2D, but glTexSubImage2D (of course, if the dimensions of the texture change, it must be glTexImage2D).
EDIT, found another possible issue, but first fix your pointer issue.
You should make sure, that you're using GL_REPLACE or GL_MODULATE texture environment mode. If using GL_DECAL or GL_BLEND you end up with red text on a red quad.
There was leaking memory of of the function in my previous post and the program was crashing after some time...
I improved this by separating the texture loading and displaying:
The first function must be called before the SDL loop.It loads text string into memory:
Every string loaded must have different txtNum parameter
GLuint texture[100];
SDL_Rect area[100];
void Load_string(char * text, SDL_Color clr, int txtNum, const char* file, int ptsize){
TTF_Font* tmpfont;
tmpfont = TTF_OpenFont(file, ptsize);
SDL_Surface *sText = SDL_DisplayFormatAlpha(TTF_RenderUTF8_Solid( tmpfont, text, clr ));
area[txtNum].x = 0;area[txtNum].y = 0;area[txtNum].w = sText->w;area[txtNum].h = sText->h;
glGenTextures(1, &texture[txtNum]);
glBindTexture(GL_TEXTURE_2D, texture[txtNum]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, sText->w, sText->h, 0, GL_BGRA, GL_UNSIGNED_BYTE, sText->pixels);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
SDL_FreeSurface( sText );
TTF_CloseFont(tmpfont);
}
The second one displays the string, must be called in the SDL loop:
void drawText(float coords[3], int txtNum) {
glBindTexture(GL_TEXTURE_2D, texture[txtNum]);
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS); {
glTexCoord2f(0, 0); glVertex3f(coords[0], coords[1], coords[2]);
glTexCoord2f(1, 0); glVertex3f(coords[0] + area[txtNum].w, coords[1], coords[2]);
glTexCoord2f(1, 1); glVertex3f(coords[0] + area[txtNum].w, coords[1] + area[txtNum].h, coords[2]);
glTexCoord2f(0, 1); glVertex3f(coords[0], coords[1] + area[txtNum].h, coords[2]);
} glEnd();
glDisable(GL_TEXTURE_2D);
}