openscad/src/OffscreenContextAll.hpp

// Functions shared by OffscreenContext[platform].cc
// #include this directly after definition of struct OffscreenContext.

#include <vector>
#include <ostream>

void bind_offscreen_context(OffscreenContext *ctx)
{
	if (ctx) fbo_bind(ctx->fbo);
}

/*
   Capture framebuffer from OpenGL and write it to the given filename as PNG.
 */
bool save_framebuffer(OffscreenContext *ctx, const char *filename)
{
	std::ofstream fstream(filename,std::ios::out|std::ios::binary);
	if (!fstream.is_open()) {
		std::cerr << "Can't open file " << filename << " for writing";
		return false;
	} else {
		save_framebuffer(ctx, fstream);
		fstream.close();
	}
	return true;
}

/*!
  Capture framebuffer from OpenGL and write it to the given ostream.
  Called by save_framebuffer() from platform-specific code.
 */
bool save_framebuffer_common(OffscreenContext *ctx, std::ostream &output)
{
	if (!ctx) return false;
	int samplesPerPixel = 4; // R, G, B and A
	std::vector<GLubyte> pixels(ctx->width * ctx->height * samplesPerPixel);
	glReadPixels(0, 0, ctx->width, ctx->height, GL_RGBA, GL_UNSIGNED_BYTE, &pixels[0]);

	// Flip it vertically - images read from OpenGL buffers are upside-down
	int rowBytes = samplesPerPixel * ctx->width;

	unsigned char *flippedBuffer = (unsigned char *)malloc(rowBytes * ctx->height);
	if (!flippedBuffer) {
		std::cerr << "Unable to allocate flipped buffer for corrected image.";
		return 1;
	}
	flip_image(&pixels[0], flippedBuffer, samplesPerPixel, ctx->width, ctx->height);

	bool writeok = write_png(output, flippedBuffer, ctx->width, ctx->height);

	free(flippedBuffer);

	return writeok;
}

//	Called by create_offscreen_context() from platform-specific code.
OffscreenContext *create_offscreen_context_common(OffscreenContext *ctx)
{
	if (!ctx) return NULL;
	GLenum err = glewInit(); // must come after Context creation and before FBO c$
	if (GLEW_OK != err) {
		std::cerr << "Unable to init GLEW: " << glewGetErrorString(err) << "\n";
		return NULL;
	}

	ctx->fbo = fbo_new();
	if (!fbo_init(ctx->fbo, ctx->width, ctx->height)) {
		return NULL;
	}

	return ctx;
}