Cinder CopyImageSubData (copies one OpenGL texture to another)

CopyImageSubData.cpp

#include "CopyImageSubData.h"

#include "cinder/gl/Texture.h"
#include "cinder/gl/Fbo.h"
#include "cinder/gl/gl.h"

namespace cinder { namespace gl {

// The copy function retreival is only tested on Windows but should work
// on other platforms as well.
void CopyImageSubData(const ci::gl::Texture& src, ci::gl::Texture& dst)
{
	typedef GLvoid(APIENTRY * PFNGLCOPYIMAGESUBDATA) (
		GLuint srcName, GLenum srcTarget, GLint srcLevel,
		GLint srcX, GLint srcY, GLint srcZ,
		GLuint dstName, GLenum dstTarget, GLint dstLevel,
		GLint dstX, GLint dstY, GLint dstZ,
		GLsizei srcWidth, GLsizei srcHeight, GLsizei srcDepth);

	// Retrieve GL_ARB_copy_image extension statically
	static struct _{
		PFNGLCOPYIMAGESUBDATA copyFn;
		_() : copyFn(nullptr) {
			if (gl::isExtensionAvailable("GL_ARB_copy_image")) {
				// Taken straight out of Glee Source:
#ifdef WIN32
				copyFn = PFNGLCOPYIMAGESUBDATA(wglGetProcAddress("glCopyImageSubData"));
#elif defined(__APPLE__) || defined(__APPLE_CC__)
				CFBundleRef bundle;
				CFURLRef bundleURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, CFSTR("/System/Library/Frameworks/OpenGL.framework"), kCFURLPOSIXPathStyle, true);

				CFStringRef functionName = CFStringCreateWithCString(kCFAllocatorDefault, "GL_ARB_copy_image", kCFStringEncodingASCII);

				void *function;

				bundle = CFBundleCreate(kCFAllocatorDefault, bundleURL);
				assert(bundle != NULL);

				function = CFBundleGetFunctionPointerForName(bundle, functionName);

				CFRelease(bundleURL);
				CFRelease(functionName);
				CFRelease(bundle);

				copyFn = PFNGLCOPYIMAGESUBDATA(function);
#else
				copyFn = PFNGLCOPYIMAGESUBDATA(glXGetProcAddressARB((const GLubyte *)"GL_ARB_copy_image"));
#endif
			}
		}
	} __;

	// Use GL_ARB_copy_image extension if available
	if (__.copyFn)
	{
		GLsizei srcDepth = src.getTarget() == GL_TEXTURE_CUBE_MAP ? 6 : 1;
		__.copyFn(src.getId(), src.getTarget(), 0, 0, 0, 0,
			dst.getId(), dst.getTarget(), 0, 0, 0, 0,
			src.getCleanWidth(), src.getCleanHeight(), srcDepth);
	}
	// Use legacy FBO copying in case GL_ARB_copy_image is not available
	else
	{
		auto fbo = ci::gl::Fbo(src.getCleanWidth(), src.getCleanHeight());
		glBindFramebuffer(GL_FRAMEBUFFER, fbo.getId());
		glFramebufferTexture2D(GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
			GL_TEXTURE_2D, src.getId(), 0);
		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT1,
			GL_TEXTURE_2D, dst.getId(), 0);
		glDrawBuffer(GL_COLOR_ATTACHMENT1);
		glBlitFramebuffer(
			0, 0, src.getCleanWidth(), src.getCleanHeight(),
			0, 0, dst.getCleanWidth(), dst.getCleanHeight(),
			GL_COLOR_BUFFER_BIT, GL_NEAREST);
	}
}

}} // namespace cinder::gl

CopyImageSubData.h

#pragma once

namespace cinder { namespace gl {
class Texture;

// Internally copies textures with FBOs if GL_ARB_copy_image ext does not exist.
void CopyImageSubData(const cinder::gl::Texture& src, cinder::gl::Texture& dst);

}} // namespace cinder::gl