Re: from NSImage to a Texture

• Subject: Re: from NSImage to a Texture
• From: Chuck Soper <email@hidden>
• Date: Tue, 30 Sep 2003 17:20:45 -0700

Use Kent's stuff or you can look at the "Cocoa OpenGL" sample as is
uses a NSImage of a string and goes to a texture in its string texture
class. See <http://developer.apple.com/opengl> for a link to the
sample.

On the list to do is a better sample that shows exactly what you are
looking for.

On Sep 28, 2003, at 7:20 PM, Kent Miller wrote:

On Sunday, September 28, 2003, at 12:00 AM,
email@hidden wrote:

Alright, ive gone throught the sample code (OpenGL Image) and im upto
the 'load an image into an NSImage ' stage. now what ? how do i get
the info i need from the NSImage into a texture to use in OpenGL ?
I had asked a similar question sometime back and i got responses
asking me to check out NSImage and NSImageRep and the 'OpenGL Image'
sample code. i've looked around at tutorials and im still unclear on
how to get from an NSImage to a texture that i can use in OpenGL.
please help :).

Someone may have a better version but this ought to get you started:


static unsigned int truncPowerOf2(unsigned int x)
{
int i = 0;
while (x = x>>1) i++;
return (1<<i);
}


void TextureFromNSImage(NSImage *image, GLuint *texID, GLuint *
width,GLuint *height)
{
NSBitmapImageRep *sourceImageRep;
GLenum imageFormat = GL_RGBA;
GLubyte *sourcePic;
long sourceRowBytes, pixelSize;
NSSize imageSize;

sourceImageRep = [[NSBitmapImageRep alloc]initWithData: [image
TIFFRepresentation]];

if ([sourceImageRep hasAlpha] == YES)
{
if ([sourceImageRep bitsPerPixel] != 32) return;
imageFormat = GL_RGBA;
pixelSize = 4;
}
else
{
if ([sourceImageRep bitsPerPixel] != 24) return;
imageFormat = GL_RGB;
pixelSize = 3;
}

sourceRowBytes = [sourceImageRep bytesPerRow];
sourcePic = (GLubyte*) [sourceImageRep bitmapData];
imageSize = [sourceImageRep size];

//Do the OpenGL flip

> {
> GLubyte *pic = malloc( imageSize.height * sourceRowBytes );
> GLuint i;
>
> for (i = 0; i < imageSize.height; i++)
> {
> memcpy ( pic + (i * sourceRowBytes),

sourcePic + ((((int)imageSize.height - i) - 1) *
sourceRowBytes),
sourceRowBytes);
}
sourcePic = pic;
}

glPixelStorei(GL_UNPACK_ROW_LENGTH, sourceRowBytes/pixelSize);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

if (*texID == 0)
glGenTextures(1, texID);
glBindTexture(GL_TEXTURE_2D,*texID);

*width = truncPowerOf2(imageSize.width);
*height = truncPowerOf2(imageSize.height);

glTexImage2D(GL_TEXTURE_2D, 0, imageFormat, *width, *height, 0,
imageFormat, GL_UNSIGNED_BYTE, sourcePic);

[sourceImageRep release];
}
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---
Geoff Stahl
3D Software Engineer
Apple
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