Macromedia

struct swf_gradient_record {
	if(f_tag == DefineMorphShape || f_tag == DefineMorphShape2) {
		unsigned char	f_position;
		swf_rgba	f_rgba;
		unsigned char	f_position_morph;
		swf_rgba	f_rgba_morph;
	}
	else if(f_tag == DefineShape3 || f_tag == DefineShape4) {
		unsigned char	f_position;
		swf_rgba	f_rgba;
	}
	else {
		unsigned char	f_position;
		swf_rgb		f_rgb;
	}
};

The first record position should be 0 and the last 255. The intermediate should use the corresponding value depending on their position in the gradient effect.

struct swf_gradient {
	if(tag == DefineShape4) {
		unsigned		f_spread_mode : 2;
		unsigned		f_interpolation_mode : 2;
		unsigned		f_count : 4;
	}
	else {
		unsigned		f_pad : 4;
		unsigned		f_count : 4;
	}
	swf_gradient_record	f_gradient_record[f_count];
	/* f_type is defined in the swf_fill_style encompassing this gradient */
	if(f_type == 0x13) {
		signed short fixed	f_focal_point;
	}
};

This structure defines a gradient. This is a set of colors which are used to define an image with colors smoothly varying from one color to the next. The gradient can be radial (circular) or linear (rectangular).

The f_count field is limited depending on the tag used and the version of SWF as defined below:

struct swf_text_record_end {
	unsigned		f_end : 8;	/* all zeroes */
};

struct swf_text_record_setup {
	unsigned		f_type_setup : 1;	/* always one */
	unsigned		f_reserved : 3;
	unsigned		f_has_font : 1;
	unsigned		f_has_color : 1;
	unsigned		f_has_move_y : 1;
	unsigned		f_has_move_x : 1;
	if(f_has_font) {
		unsigned short		f_font_id_ref;
	}
	if(f_has_color) {
		if(tag == DefineText) {
			swf_rgb		f_color;
		}
		else {	/* if tag is DefineText2 */
			swf_rgba	f_color;
		}
	}
	if(f_has_move_x) {
		signed short		f_move_x;
	}
	if(f_has_move_y) {
		signed short		f_move_y;
	}
	if(f_has_font) {
		unsigned short		f_font_height;
	}
};

struct swf_text_record_glyphs {
	unsigned		f_type_glyph : 1;		/* always zero */
	unsigned		f_glyph_count : 7;		/* at least one */
	swf_text_entry		f_entry[f_glyph_count];
};

struct swf_text_record_string {
	unsigned		f_type_setup : 1;	/* always one */
	unsigned		f_reserved : 3;
	unsigned		f_has_font : 1;
	unsigned		f_has_color : 1;
	unsigned		f_has_move_y : 1;
	unsigned		f_has_move_x : 1;
	if(f_has_font) {
		unsigned short		f_font_id_ref;
	}
	if(f_has_color) {
		if(tag == DefineText) {
			swf_rgb		f_color;
		}
		else {	/* if tag is DefineText2 */
			swf_rgba	f_color;
		}
	}
	if(f_has_move_x) {
		signed short		f_move_x;
	}
	if(f_has_move_y) {
		signed short		f_move_y;
	}
	if(f_has_font) {
		unsigned short		f_font_height;
	}
	unsigned char		f_glyph_count;		/* at least one */
	swf_text_entry		f_entry[f_glyph_count];
};

union swf_text_record {
	unsigned		f_flags : 8;
	swf_text_record_end	f_end;
	if(version >= 7) {
		swf_text_record_string	f_string;
	}
	else {
		swf_text_record_setup	f_setup;
		swf_text_record_glyphs	f_glyphs;
	}
};

The swf_text_record structure is a union composed of a swf_text_record_setup definition followed by characters. Multiple records can follow each others. The list is ended with one byte set to 0.

WARNING: it seems that Macromedia didn't think about a file having two records of type glyph one after another (it makes their plugins crash); you will have to insert a setup record between each glyph record (the setup can be empty: i.e. add one byte equal to 0x80). The very first setup has to at least define the font.

NOTE: this has been corrected by Macromedia it now shows as one structure ...

Apparently, Macromedia thought that synchronizing their animation with, probably, the VLB would be a good idea. Yet they dropped it and never released that out. It is probably not useful for animations (visual) to be properly synchronize when there is not audio. If you do have audio, you should synchronize the animation to the audio and drop visual frames as required to keep up with the audio.

struct swf_placeobject2 {	/* and swf_placeobject3 */
	swf_tag			f_tag;		/* 26 or 70 */
	/* NOTE: the following flags can be read as one or two bytes also */
	if(version >= 8) {
		unsigned	f_place_reserved : 5;
		unsigned	f_place_bitmap_caching : 1;
		unsigned	f_place_blend_mode : 1;
		unsigned	f_place_filters : 1;
	}
	if(version >= 5) {
		unsigned	f_place_has_actions : 1;
	}
	else {
		unsigned	f_place_reserved : 1;
	}
	unsigned		f_place_has_clipping_depth : 1;
	unsigned		f_place_has_name : 1;
	unsigned		f_place_has_morph_position : 1;
	unsigned		f_place_has_color_transform : 1;
	unsigned		f_place_has_matrix : 1;
	unsigned		f_place_has_id_ref : 1;
	unsigned		f_place_has_move : 1;
	unsigned short		f_depth;
	if(f_place_has_id_ref) {
		unsigned short		f_object_id_ref;
	}
	if(f_place_has_matrix) {
		swf_matrix		f_matrix;
	}
	if(f_place_has_color_transform) {
		swf_color_transform	f_color_transform;
	}
	if(f_place_has_morph_position) {
		unsigned short		f_morph_position;
	}
	if(f_place_has_name) {
		string			f_name;
	}
	if(f_place_has_clipping_depth) {
		unsigned short		f_clipping_depth;
	}
	/* 3 next entries since v8.0 */
	if(f_place_filters) {
		unsigned char		f_filter_count;
		swf_any_filter		f_filter;
	}
	if(f_place_blend_mode) {
		unsigned char		f_blend_mode;
	}
	if(f_place_bitmap_caching) {
		/* WARNING: this is not defined in the Macromedia documentation
		 * it may be that it was part of the blend mode whenever the person
		 * who defined this byte was testing (I copied that from somewhere else!).
		 */
		unsigned char		f_bitmap_caching;
	}
	/* since v5.0 */
	if(f_place_has_actions) {
		unsigned short		f_reserved;
		if(version >= 6) {
			unsigned long	f_all_flags;
		}
		else {
			unsigned short	f_all_flags;
		}
		swf_event		f_event[<variable>];
		if(version >= 6) {
			unsigned long	f_end;	/* always zero */
		}
		else {
			unsigned short	f_end;	/* always zero */
		}
	}
};

This tag will be used to specify where and how to place an object in the next frame. The PlaceObject is much different and is presented separately.

The f_depth field is used to indicate at which depth the character is inserted in the current frame. There can be only one object per depth value (thus a maximum of 65536 objects can appear on a single frame).

The f_place_has_move and f_place_has_id_ref flags are used to indicate what to do at the given depth. The following table presents what happens depending on the current value.

f_place_has_move	...

struct swf_protect {
	swf_tag			f_tag;		/* 24, 58 or 64  */
	if(version >= 5) {
		if(tag == ProtectDebug2) {
			unsigned short	f_reserved;
		}
		/* the password is optional when tag == Protect */
		string		f_md5_password;
	}
};

The protection tag is totally useless. The SWF format is an open format, otherwise how would you have so many players and tools to work with SWF movies? Thus, you can pretend to protect your movies, but anyone with a simple binary editor can transform the tag and make it another which has no such effect. Also, swf_dump and some other tools (such as flasm) can read your movie anyway.

For the sake of defining what you have in each tag, there are the protection tags fully described.

According to Macromedia, you can find some free implementation of the MD5 algorithm by Poul-Henning Kamp in ...

struct swf_doaction {
	swf_tag			f_tag;		/* 12 and 59 */
	if(f_tag == DoInitAction) {
		unsigned short	f_action_sprite;
	}
	swf_action		f_action_record[variable];
};

The DoAction tag will be used to execute a set of actions in place. Usually, actions are used on buttons to add interactivity to the SWF movies. In version 1 you had only one dynamic branch (WaitForFrame). In version 4 you can test many different things such as a position, angle or sound track cursor position. Since version 5, SWF has a complete scripting language supporting string and arithmetic operations.

struct swf_setbackgroundcolor {
	swf_tag			f_tag;		/* 9 */
	swf_rgb			f_rgb;
};

This tag is used to specify the background color. It should always be included at the start of every .swf file (after the FileAttributes and Protect tags). Only an RGB color can be used (i.e. there is no alpha channel for that color, whatever the SWF version.)

To create a Flash animation that's transparent (so we can see the website gradient, for example) you use the wmode parameter in the HTML tag with the value "transparent", in which case the background color will be ignored and replaced by a fully transparent background. For example:

<embed width="440"  ...

Brief History

At the very beginning, a company created the SWF format to generate small vector animations on the Internet called Shockwave Flash (hence the name of the format, SWF.) It also included images. This company was bought by Macromedia around 1997 (if I recall properly). This is when Flash v3 was created. Since then, Macromedia created a new version about once a year up to version 8. At that time (in 2005/2006), Macromedia sealed a deal with Adobe which wanted to use the SWF format in their PDF files.

Today (May 1st, 2008), the SWF format is available for free to all.

There was ...

SSWF™ name

The name SSWF™ is used by Made to Order Software to reference its SWF library. You are welcome to use this name in reference the SSWF library if you use it in your own software.

SWF Format

Please, note that there is no restriction in using this document. However, the SWF format copyright holders are Macromedia and Adobe. There may be limits in what you can do using this format. If you are not sure, I suggest you contact a knowledgeable copyright and Software attorney who can help you decide what you can do with the SWF format.