Draw 2-Dimensional Image 32bit - opengl

Question

I'm trying to draw a buffer of pixels to the screen. When I draw, black is drawn as transparent which is perfect. However, other colours are also drawn transparent. I cannot seem to figure out why.
I draw using:
glDrawPixels(width, height, GL_BGRA, GL_UNSIGNED_BYTE, buffer);
to draw a 32 bit bmp. However, the bitmap does not show unless I do convert it to 24 bit and use GL_BGR. Am I doing something wrong? Is there a reason black would be transparent?
Right before doing a draw, I do:
void Enable2DDrawing(bool &DrawingEnabled, bool &GLTexture2D, bool &GLRectangleTexture, bool &PointSmooth, float &PointSize)
{
if (!DrawingEnabled)
{
GLTexture2D = glIsEnabled(GL_TEXTURE_2D);
GLRectangleTexture = glIsEnabled(GL_TEXTURE_RECTANGLE);
PointSmooth = glIsEnabled(GL_POINT_SMOOTH);
glGetFloatv(GL_POINT_SIZE, &PointSize);
glDisable(GL_TEXTURE_RECTANGLE);
glDisable(GL_TEXTURE_2D);
glEnable(GL_POINT_SMOOTH);
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
glPushMatrix();
glLoadIdentity();
DrawingEnabled = true;
}
}
and right after drawing, I do:
void Disable2DDrawing(bool &DrawingEnabled, bool GLTexture2D, bool GLRectangleTexture, bool PointSmooth, float PointSize)
{
if (DrawingEnabled)
{
glPopMatrix();
if (GLTexture2D) glEnable(GL_TEXTURE_2D);
if (GLRectangleTexture) glEnable(GL_TEXTURE_RECTANGLE);
if (PointSmooth) glDisable(GL_POINT_SMOOTH);
DrawingEnabled = false;
}
}
Then I swap the buffer. I also tried drawing using textures by doing:
GLuint LoadTexture(void* Buffer, int width, int height, GLenum Target)
{
GLuint ID = 0;
glGenTextures(1, &ID);
glBindTexture(Target, ID);
glTexParameteri(Target, GL_TEXTURE_WRAP_S, Target == GL_TEXTURE_2D ? GL_REPEAT : GL_CLAMP_TO_EDGE);
glTexParameteri(Target, GL_TEXTURE_WRAP_T, Target == GL_TEXTURE_2D ? GL_REPEAT : GL_CLAMP_TO_EDGE);
glTexParameteri(Target, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(Target, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(Target, 0, GL_RGBA, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, Buffer);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
return ID;
}
void DrawTexture(std::uint32_t Target, std::uint32_t ID, float X1, float Y1, float X2, float Y2, int Width, int Height)
{
Width = Target == GL_TEXTURE_RECTANGLE ? Width : 1;
Height = Target == GL_TEXTURE_RECTANGLE ? Height : 1;
glEnable(Target);
glBindTexture(Target, ID);
glBegin(GL_QUADS);
glTexCoord2f(0, Height);
glVertex2f(X1, Y1); //top left
glTexCoord2f(0, 0); //bottom left
glVertex2f(X1, Y2);
glTexCoord2f(Width, 0);
glVertex2f(X2, Y2); //bottom right
glTexCoord2f(Width, Height);
glVertex2f(X2, Y1); //top right
glEnd();
glDisable(Target);
}
But it does not draw the bitmap correctly. It draws a 32-bit bmp like:
http://i.imgur.com/A4pE2Uw.png when it is supposed to be completely white. If I draw each pixel 1 by 1, it works fine. Am I missing something?
What is the best way to draw 32 bit bitmaps and do I have to use glPixelStorei? Does anyone have sample code for drawing a bitmap or a nice explanation on how?

Answer 1

Have you enabled blending?
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);