Module: NL::FastPng::PngExt

Defined in:
ext/nl-fast_png/png_ext.c

Class Method Summary collapse

Class Method Details

.store_png(width, height, depth, data) ⇒ Object

compression). 16-bit data is expected to be in little-endian order.



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# File 'ext/nl-fast_png/png_ext.c', line 92

VALUE rb_store_png(VALUE self, VALUE width, VALUE height, VALUE depth, VALUE data)
{
	VALUE outbuf;
	VALUE errstr;
	VALUE ret;

	unsigned int w, h, d;
	png_structp png_ptr;
	png_infop info_ptr;

	Check_Type(data, T_STRING);
	w = NUM2UINT(width);
	h = NUM2UINT(height);
	d = NUM2UINT(depth);

	if(d != 8 && d != 16) {
		rb_raise(rb_eArgError, "Depth must be either 8 or 16 (got %u).", d);
	}

	if(RSTRING_LEN(data) < w * h * (d / 8)) {
		rb_raise(rb_eArgError, "Data must contain at least %u bytes (got %zd).", w * h * (d / 8), (ssize_t)RSTRING_LEN(data));
	}

	outbuf = rb_str_buf_new(0);

	if(!(png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, &errstr, error_func, warn_func))) {
		rb_raise(rb_eStandardError, "Unable to create PNG writing structure: %s\n", RSTRING_PTR(errstr));
	}

	if(!(info_ptr = png_create_info_struct(png_ptr))) {
		png_destroy_write_struct(&png_ptr, NULL);
		rb_raise(rb_eStandardError, "Unable to create PNG info structure: %s\n", RSTRING_PTR(errstr));
	}

	if(setjmp(png_jmpbuf(png_ptr))) {
		png_destroy_write_struct(&png_ptr, &info_ptr);
		rb_raise(rb_eStandardError, "A libpng error occurred: %s\n", RSTRING_PTR(errstr));
	}

	png_set_write_fn(png_ptr, &outbuf, write_func, flush_func);

	png_set_IHDR(png_ptr, info_ptr, w, h, d,
		     PNG_COLOR_TYPE_GRAY, PNG_INTERLACE_NONE,
		     PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

	png_set_filter(png_ptr, 0, PNG_FILTER_SUB);
	png_set_compression_level(png_ptr, Z_BEST_SPEED);

	png_write_info(png_ptr, info_ptr);

	// FIXME: this is accessing a Ruby string's contents without the GVL; is that a problem?
	ret = rb_thread_call_without_gvl(
			store_png_blocking,
			&(struct kinpng_info){
			.w = w, .h = h, .d = d, .data = RSTRING_PTR(data), .png_ptr = png_ptr, .info_ptr = info_ptr
			},
			NULL,
			NULL
			);
	if(ret == NULL) {
		rb_raise(rb_eStandardError, "A libpng error occurred while writing: %s\n", RSTRING_PTR(errstr));
	}

	if(setjmp(png_jmpbuf(png_ptr))) {
		rb_raise(rb_eStandardError, "A libpng error occurred: %s\n", RSTRING_PTR(errstr));
	}

	png_destroy_write_struct(&png_ptr, &info_ptr);

	return outbuf;
}