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skills/slack-gif-creator/core/gif_builder.py

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+#!/usr/bin/env python3
+"""
+GIF Builder - Core module for assembling frames into GIFs optimized for Slack.
+
+This module provides the main interface for creating GIFs from programmatically
+generated frames, with automatic optimization for Slack's requirements.
+"""
+
+from pathlib import Path
+from typing import Optional
+import imageio.v3 as imageio
+from PIL import Image
+import numpy as np
+
+
+class GIFBuilder:
+    """Builder for creating optimized GIFs from frames."""
+
+    def __init__(self, width: int = 480, height: int = 480, fps: int = 15):
+        """
+        Initialize GIF builder.
+
+        Args:
+            width: Frame width in pixels
+            height: Frame height in pixels
+            fps: Frames per second
+        """
+        self.width = width
+        self.height = height
+        self.fps = fps
+        self.frames: list[np.ndarray] = []
+
+    def add_frame(self, frame: np.ndarray | Image.Image):
+        """
+        Add a frame to the GIF.
+
+        Args:
+            frame: Frame as numpy array or PIL Image (will be converted to RGB)
+        """
+        if isinstance(frame, Image.Image):
+            frame = np.array(frame.convert('RGB'))
+
+        # Ensure frame is correct size
+        if frame.shape[:2] != (self.height, self.width):
+            pil_frame = Image.fromarray(frame)
+            pil_frame = pil_frame.resize((self.width, self.height), Image.Resampling.LANCZOS)
+            frame = np.array(pil_frame)
+
+        self.frames.append(frame)
+
+    def add_frames(self, frames: list[np.ndarray | Image.Image]):
+        """Add multiple frames at once."""
+        for frame in frames:
+            self.add_frame(frame)
+
+    def optimize_colors(self, num_colors: int = 128, use_global_palette: bool = True) -> list[np.ndarray]:
+        """
+        Reduce colors in all frames using quantization.
+
+        Args:
+            num_colors: Target number of colors (8-256)
+            use_global_palette: Use a single palette for all frames (better compression)
+
+        Returns:
+            List of color-optimized frames
+        """
+        optimized = []
+
+        if use_global_palette and len(self.frames) > 1:
+            # Create a global palette from all frames
+            # Sample frames to build palette
+            sample_size = min(5, len(self.frames))
+            sample_indices = [int(i * len(self.frames) / sample_size) for i in range(sample_size)]
+            sample_frames = [self.frames[i] for i in sample_indices]
+
+            # Combine sample frames into a single image for palette generation
+            # Flatten each frame to get all pixels, then stack them
+            all_pixels = np.vstack([f.reshape(-1, 3) for f in sample_frames])  # (total_pixels, 3)
+
+            # Create a properly-shaped RGB image from the pixel data
+            # We'll make a roughly square image from all the pixels
+            total_pixels = len(all_pixels)
+            width = min(512, int(np.sqrt(total_pixels)))  # Reasonable width, max 512
+            height = (total_pixels + width - 1) // width  # Ceiling division
+
+            # Pad if necessary to fill the rectangle
+            pixels_needed = width * height
+            if pixels_needed > total_pixels:
+                padding = np.zeros((pixels_needed - total_pixels, 3), dtype=np.uint8)
+                all_pixels = np.vstack([all_pixels, padding])
+
+            # Reshape to proper RGB image format (H, W, 3)
+            img_array = all_pixels[:pixels_needed].reshape(height, width, 3).astype(np.uint8)
+            combined_img = Image.fromarray(img_array, mode='RGB')
+
+            # Generate global palette
+            global_palette = combined_img.quantize(colors=num_colors, method=2)
+
+            # Apply global palette to all frames
+            for frame in self.frames:
+                pil_frame = Image.fromarray(frame)
+                quantized = pil_frame.quantize(palette=global_palette, dither=1)
+                optimized.append(np.array(quantized.convert('RGB')))
+        else:
+            # Use per-frame quantization
+            for frame in self.frames:
+                pil_frame = Image.fromarray(frame)
+                quantized = pil_frame.quantize(colors=num_colors, method=2, dither=1)
+                optimized.append(np.array(quantized.convert('RGB')))
+
+        return optimized
+
+    def deduplicate_frames(self, threshold: float = 0.995) -> int:
+        """
+        Remove duplicate or near-duplicate consecutive frames.
+
+        Args:
+            threshold: Similarity threshold (0.0-1.0). Higher = more strict (0.995 = very similar).
+
+        Returns:
+            Number of frames removed
+        """
+        if len(self.frames) < 2:
+            return 0
+
+        deduplicated = [self.frames[0]]
+        removed_count = 0
+
+        for i in range(1, len(self.frames)):
+            # Compare with previous frame
+            prev_frame = np.array(deduplicated[-1], dtype=np.float32)
+            curr_frame = np.array(self.frames[i], dtype=np.float32)
+
+            # Calculate similarity (normalized)
+            diff = np.abs(prev_frame - curr_frame)
+            similarity = 1.0 - (np.mean(diff) / 255.0)
+
+            # Keep frame if sufficiently different
+            # High threshold (0.995) means only remove truly identical frames
+            if similarity < threshold:
+                deduplicated.append(self.frames[i])
+            else:
+                removed_count += 1
+
+        self.frames = deduplicated
+        return removed_count
+
+    def save(self, output_path: str | Path, num_colors: int = 128,
+             optimize_for_emoji: bool = False, remove_duplicates: bool = True) -> dict:
+        """
+        Save frames as optimized GIF for Slack.
+
+        Args:
+            output_path: Where to save the GIF
+            num_colors: Number of colors to use (fewer = smaller file)
+            optimize_for_emoji: If True, optimize for <64KB emoji size
+            remove_duplicates: Remove duplicate consecutive frames
+
+        Returns:
+            Dictionary with file info (path, size, dimensions, frame_count)
+        """
+        if not self.frames:
+            raise ValueError("No frames to save. Add frames with add_frame() first.")
+
+        output_path = Path(output_path)
+        original_frame_count = len(self.frames)
+
+        # Remove duplicate frames to reduce file size
+        if remove_duplicates:
+            removed = self.deduplicate_frames(threshold=0.98)
+            if removed > 0:
+                print(f"  Removed {removed} duplicate frames")
+
+        # Optimize for emoji if requested
+        if optimize_for_emoji:
+            if self.width > 128 or self.height > 128:
+                print(f"  Resizing from {self.width}x{self.height} to 128x128 for emoji")
+                self.width = 128
+                self.height = 128
+                # Resize all frames
+                resized_frames = []
+                for frame in self.frames:
+                    pil_frame = Image.fromarray(frame)
+                    pil_frame = pil_frame.resize((128, 128), Image.Resampling.LANCZOS)
+                    resized_frames.append(np.array(pil_frame))
+                self.frames = resized_frames
+            num_colors = min(num_colors, 48)  # More aggressive color limit for emoji
+
+            # More aggressive FPS reduction for emoji
+            if len(self.frames) > 12:
+                print(f"  Reducing frames from {len(self.frames)} to ~12 for emoji size")
+                # Keep every nth frame to get close to 12 frames
+                keep_every = max(1, len(self.frames) // 12)
+                self.frames = [self.frames[i] for i in range(0, len(self.frames), keep_every)]
+
+        # Optimize colors with global palette
+        optimized_frames = self.optimize_colors(num_colors, use_global_palette=True)
+
+        # Calculate frame duration in milliseconds
+        frame_duration = 1000 / self.fps
+
+        # Save GIF
+        imageio.imwrite(
+            output_path,
+            optimized_frames,
+            duration=frame_duration,
+            loop=0  # Infinite loop
+        )
+
+        # Get file info
+        file_size_kb = output_path.stat().st_size / 1024
+        file_size_mb = file_size_kb / 1024
+
+        info = {
+            'path': str(output_path),
+            'size_kb': file_size_kb,
+            'size_mb': file_size_mb,
+            'dimensions': f'{self.width}x{self.height}',
+            'frame_count': len(optimized_frames),
+            'fps': self.fps,
+            'duration_seconds': len(optimized_frames) / self.fps,
+            'colors': num_colors
+        }
+
+        # Print info
+        print(f"\n✓ GIF created successfully!")
+        print(f"  Path: {output_path}")
+        print(f"  Size: {file_size_kb:.1f} KB ({file_size_mb:.2f} MB)")
+        print(f"  Dimensions: {self.width}x{self.height}")
+        print(f"  Frames: {len(optimized_frames)} @ {self.fps} fps")
+        print(f"  Duration: {info['duration_seconds']:.1f}s")
+        print(f"  Colors: {num_colors}")
+
+        # Warnings
+        if optimize_for_emoji and file_size_kb > 64:
+            print(f"\n⚠️  WARNING: Emoji file size ({file_size_kb:.1f} KB) exceeds 64 KB limit")
+            print("   Try: fewer frames, fewer colors, or simpler design")
+        elif not optimize_for_emoji and file_size_kb > 2048:
+            print(f"\n⚠️  WARNING: File size ({file_size_kb:.1f} KB) is large for Slack")
+            print("   Try: fewer frames, smaller dimensions, or fewer colors")
+
+        return info
+
+    def clear(self):
+        """Clear all frames (useful for creating multiple GIFs)."""
+        self.frames = []