Screenshots in openGL/SDL fullscreen
Post: #1
Hi,
I'm hard (
) at work on my uDG entry and I would like to show off a bit. Does anyone have any info on how I can make a screen shot, or even simply make a function like getRGB_Pixel_From_Render_Buffer(int x,int y, &r,&g,&b); or something. Anyone?
Thanks.
I'm hard (
) at work on my uDG entry and I would like to show off a bit. Does anyone have any info on how I can make a screen shot, or even simply make a function like getRGB_Pixel_From_Render_Buffer(int x,int y, &r,&g,&b); or something. Anyone?Thanks.
Post: #3
So I would use it like this?:
unsigned int pixel[4];
glReadPixels(x,y,1,1,GL_RGBA,GL_UNSIGNED_INT_8_8_8_8,& pixel);
unsigned int pixel[4];
glReadPixels(x,y,1,1,GL_RGBA,GL_UNSIGNED_INT_8_8_8_8,& pixel);
Post: #4
Here's the code I use, which is from Hardwarie, which handles the hardware side of drawing for SpriteWorld. I've just copy/pasted the entire function so you can get an idea. You'll need to strip out some of the Hardwarie specific stuff to get it to compile.
If you have any questions, let me know.
And SpriteWorld 3.0.1 should be out any day now, btw
If you have any questions, let me know.
And SpriteWorld 3.0.1 should be out any day now, btw
Code:
OSErr HardwarieCopyContextToGWorld (
HardwarieContextPtr hardwareContextP,
GWorldPtr *gworldBufferP,
RectPtr copyRectP)
{
OSErr err = noErr;
char *dataBuffer;
long dataRowBytes;
Rect newRect;
PixMapHandle pix;
GLRect glRect;
GLenum glerr;
*gworldBufferP = NULL;
HARDWARE_ASSERT( hardwareContextP != NULL );
HARDWARE_ASSERT( copyRectP != NULL );
if (hardwareContextP == NULL || hardwareContextP->context == NULL)
return -1; // error code ?
if (!hardwareContextP->contextActive)
return -1; // error code ?
glFinish();
if (copyRectP == NULL)
{
newRect.left = newRect.top = 0;
newRect.right = hardwareContextP->width;
newRect.bottom = hardwareContextP->height;
}
else
{
newRect = *copyRectP;
}
glRect.x = newRect.left;
glRect.y = hardwareContextP->height - newRect.bottom;
glRect.width = newRect.right - newRect.left;
glRect.height = newRect.bottom - newRect.top;
glRect.center.x = glRect.width / 2;
glRect.center.y = glRect.height / 2;
// Alloc enough memory for this data
dataRowBytes = glRect.width * 4;
dataBuffer = (char *) NewPtr(glRect.height * dataRowBytes);
if (dataBuffer == NULL)
return memFullErr;
// Read the back buffer
// (glReadBuffer() is set to GL_BACK by default in a double buffered context)
glReadBuffer(GL_BACK);
glReadPixels (glRect.x, glRect.y, glRect.width, glRect.height,
GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, dataBuffer);
glerr = glGetError();
if(glerr == GL_NO_ERROR)
{
err = NewGWorld(gworldBufferP, 32, &newRect, (CTabHandle) NULL, (GDHandle) NULL, 0L);
if (err == noErr)
{
unsigned long *src,*dst;
long srcStride,dstStride;
int x,y;
pix = GetGWorldPixMap(*gworldBufferP);
LockPixels(pix);
src = (unsigned long *) dataBuffer;
srcStride = dataRowBytes;
dst = (unsigned long *) GetPixBaseAddr(pix);
dstStride = GetPixRowBytes(pix);
// flip vertical
dst = (unsigned long *) (((unsigned char *) dst) + (glRect.height - 1) * dstStride);
dstStride = -dstStride;
srcStride -= glRect.width * sizeof(unsigned long);
dstStride -= glRect.width * sizeof(unsigned long);
for (y = 0; y < glRect.height; y++)
{
for (x = 0; x < glRect.width; x++)
{
// convert RGBA32 to RGB32
*dst++ = (*src++ >> 8);
}
src = (unsigned long *) (((unsigned char *) src) + srcStride);
dst = (unsigned long *) (((unsigned char *) dst) + dstStride);
}
PortChanged((GrafPtr) *gworldBufferP);
UnlockPixels(pix);
}
}
else
err = glerr;
DisposePtr((Ptr) dataBuffer);
return err;
}
Post: #5
In general, if you're reading back a lot of data, it's best to do it in one big chunk, not individual pixels one at a time scattered around. glReadPixels has a very significant performance hit per call.
Post: #6
this is for screenshots so I really don't care about how long it takes. 1 second for a screenshot is fine, and I doubt it would take that.
Post: #7Joseph Duchesne Wrote:1 second for a screenshot is fine, and I doubt it would take that.
I don't...
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