ZSM File Format Specification

ZSpriteMaker Project File format (.zsm) - used by ZSpriteMaker for ALttP custom sprites.

Source: ~/Documents/Zelda/Editors/ZSpriteMaker-1/

Format Overview

Binary file format using .NET BinaryWriter/BinaryReader conventions:

• Strings: Length-prefixed (7-bit encoded length + UTF-8 bytes)
• Integers: Little-endian 32-bit
• Booleans: Single byte (0x00 = false, 0x01 = true)

File Structure

┌─────────────────────────────────────────────────┐
│ ANIMATIONS SECTION                              │
├─────────────────────────────────────────────────┤
│ int32     animationCount                        │
│ for each animation:                             │
│   string  name         (length-prefixed)        │
│   byte    frameStart                            │
│   byte    frameEnd                              │
│   byte    frameSpeed                            │
├─────────────────────────────────────────────────┤
│ FRAMES SECTION                                  │
├─────────────────────────────────────────────────┤
│ int32     frameCount                            │
│ for each frame:                                 │
│   int32   tileCount                             │
│   for each tile:                                │
│     uint16  id         (tile index in sheet)    │
│     byte    palette    (0-7)                    │
│     bool    mirrorX                             │
│     bool    mirrorY                             │
│     byte    priority   (0-3, default 3)         │
│     bool    size       (false=8x8, true=16x16)  │
│     byte    x          (0-251)                  │
│     byte    y          (0-219)                  │
│     byte    z          (depth/layer)            │
├─────────────────────────────────────────────────┤
│ SPRITE PROPERTIES (20 booleans)                 │
├─────────────────────────────────────────────────┤
│ bool      blockable                             │
│ bool      canFall                               │
│ bool      collisionLayer                        │
│ bool      customDeath                           │
│ bool      damageSound                           │
│ bool      deflectArrows                         │
│ bool      deflectProjectiles                    │
│ bool      fast                                  │
│ bool      harmless                              │
│ bool      impervious                            │
│ bool      imperviousArrow                       │
│ bool      imperviousMelee                       │
│ bool      interaction                           │
│ bool      isBoss                                │
│ bool      persist                               │
│ bool      shadow                                │
│ bool      smallShadow                           │
│ statis    (stasis)                              │
│ bool      statue                                │
│ bool      waterSprite                           │
├─────────────────────────────────────────────────┤
│ SPRITE STATS (6 bytes)                          │
├─────────────────────────────────────────────────┤
│ byte      prize       (drop item ID)            │
│ byte      palette     (sprite palette)          │
│ byte      oamNbr      (OAM slot count)          │
│ byte      hitbox      (collision box ID)        │
│ byte      health                                │
│ byte      damage                                │
├─────────────────────────────────────────────────┤
│ USER ROUTINES SECTION (optional)                │
├─────────────────────────────────────────────────┤
│ string    spriteName  (length-prefixed)         │
│ int32     routineCount                          │
│ for each routine:                               │
│   string  name        (e.g., "Long Main")       │
│   string  code        (ASM code)                │
├─────────────────────────────────────────────────┤
│ SPRITE ID (optional)                            │
├─────────────────────────────────────────────────┤
│ string    spriteId    (hex string)              │
└─────────────────────────────────────────────────┘

Data Types

OamTile

struct OamTile {
    uint16_t id;        // Tile index in sprite sheet (0-511)
    uint8_t  palette;   // Palette index (0-7)
    bool     mirrorX;   // Horizontal flip
    bool     mirrorY;   // Vertical flip
    uint8_t  priority;  // BG priority (0-3)
    bool     size;      // false=8x8, true=16x16
    uint8_t  x;         // X position (0-251)
    uint8_t  y;         // Y position (0-219)
    uint8_t  z;         // Z depth for sorting
};
 
// Tile sheet position from ID:
// sheet_x = (id % 16) * 8
// sheet_y = (id / 16) * 8

AnimationGroup

struct AnimationGroup {
    std::string name;       // Animation name
    uint8_t     frameStart; // First frame index
    uint8_t     frameEnd;   // Last frame index
    uint8_t     frameSpeed; // Frames per tick
};

Frame

struct Frame {
    std::vector<OamTile> tiles;
};

Sprite Properties Bitfield (Alternative)

The 20 boolean properties could be packed as bitfield:

enum SpriteFlags : uint32_t {
    BLOCKABLE           = 1 << 0,
    CAN_FALL            = 1 << 1,
    COLLISION_LAYER     = 1 << 2,
    CUSTOM_DEATH        = 1 << 3,
    DAMAGE_SOUND        = 1 << 4,
    DEFLECT_ARROWS      = 1 << 5,
    DEFLECT_PROJECTILES = 1 << 6,
    FAST                = 1 << 7,
    HARMLESS            = 1 << 8,
    IMPERVIOUS          = 1 << 9,
    IMPERVIOUS_ARROW    = 1 << 10,
    IMPERVIOUS_MELEE    = 1 << 11,
    INTERACTION         = 1 << 12,
    IS_BOSS             = 1 << 13,
    PERSIST             = 1 << 14,
    SHADOW              = 1 << 15,
    SMALL_SHADOW        = 1 << 16,
    STASIS              = 1 << 17,
    STATUE              = 1 << 18,
    WATER_SPRITE        = 1 << 19,
};

Default User Routines

New projects include three template routines:

1. Long Main - Main sprite loop (TemplateLongMain.asm)
2. Sprite Prep - Initialization (TemplatePrep.asm)
3. Sprite Draw - Rendering (TemplateDraw.asm)

Related Formats

ZSPR (ALttP Randomizer Format)

Different format used by ALttP Randomizer for Link sprite replacements.

• Magic: ZSPR (4 bytes)
• Contains: sprite sheet, palette, glove colors, metadata
• Spec: https://github.com/Zarby89/ZScreamRandomizer

ZSM vs ZSPR

Feature	ZSM	ZSPR
Purpose	Custom enemy/NPC sprites	Link sprite replacement
Contains ASM	Yes (routines)	No
Animation data	Yes	No (uses ROM animations)
Properties	Sprite behavior flags	Metadata only
Editor	ZSpriteMaker	SpriteSomething, others

Implementation Notes

Reading ZSM in C++

// .NET BinaryReader string format:
std::string read_dotnet_string(std::istream& is) {
    uint32_t length = 0;
    uint8_t byte;
    int shift = 0;
    do {
        is.read(reinterpret_cast<char*>(&byte), 1);
        length |= (byte & 0x7F) << shift;
        shift += 7;
    } while (byte & 0x80);
 
    std::string result(length, '\0');
    is.read(&result[0], length);
    return result;
}

Validation

• Frame count typically 0-255 (byte range in UI)
• Tile positions clamped: x < 252, y < 220
• Palette 0-7
• Priority 0-3

Source Files

From ~/Documents/Zelda/Editors/ZSpriteMaker-1/ZSpriteMaker/:

• MainWindow.xaml.cs:323-419 - Save_Command (write format)
• MainWindow.xaml.cs:209-319 - Open_Command (read format)
• OamTile.cs - Tile data structure
• Frame.cs - Frame container
• AnimationGroup.cs - Animation definition