Method transformAnimated

processing/processing.go:376–496

(
	ctx context.Context,
	img *vips.Image,
	po ProcessingOptions,
)

}

func (p *Processor) transformAnimated(
	ctx context.Context,
	img *vips.Image,
	po ProcessingOptions,
) error {
	if po.TrimEnabled() {
		slog.Warn("Trim is not supported for animated images")
		po.DisableTrim()
	}

	imgWidth := img.Width()
	frameHeight := img.PageHeight()
	framesCount := img.PagesLoaded()

	// Get frame delays. We'll need to set them back later.
	// If we don't have delay info, we'll set a default delay later.
	delay, err := img.GetIntSliceDefault("delay", nil)
	if err != nil {
		return err
	}

	// Get loop count. We'll need to set it back later.
	// 0 means infinite looping.
	loop, err := img.GetIntDefault("loop", 0)
	if err != nil {
		return err
	}

	// Disable watermarking for individual frames.
	// It's more efficient to apply watermark to all frames at once after they are processed.
	watermarkOpacity := po.WatermarkOpacity()
	if watermarkOpacity > 0 {
		po.DeleteWatermarkOpacity()
		defer func() { po.SetWatermarkOpacity(watermarkOpacity) }()
	}

	// Make a slice to hold processed frames and ensure they are cleared on function exit
	frames := make([]*vips.Image, 0, framesCount)
	defer func() {
		for _, frame := range frames {
			if frame != nil {
				frame.Clear()
			}
		}
	}()

	for i := range framesCount {
		frame := new(vips.Image)

		// Extract an individual frame from the image.
		// Libvips loads animated images as a single image with frames stacked vertically.
		if err = img.Extract(frame, 0, i*frameHeight, imgWidth, frameHeight); err != nil {
			return err
		}

		frames = append(frames, frame)

		// Transform the frame using the main pipeline.