PngSaver

class io.savers.PngSaver

Bases: io.savers.BaseSaver

PNGSAVER - Saver for Portable Network Graphics (PNG) output.

PNG is a lossless raster format. Because PNG files are inherently 2-D, every Z-slice is saved as a separate file (always sequence mode). Multichannel data with more than 3 colour channels is not supported (PNG maximum = 3 channels + optional alpha).

Handled format strings: ‘Portable Network Graphics (*.png)’ - used when saving image layer ‘PNG format (*.png)’ - alias used for mask/labels

DATA DIMENSIONS Input data : [H, W, D, C, T] imwrite call: [H, W, C] per 2-D slice (Z and T loops)

NOTES * For indexed images metadata.colormap (or metadata.lutColors) is used as the colour table. * Resolution metadata (pixels/unit) is stored in the PNG file if metadata.xResolution and metadata.yResolution are provided. * When options.FilenameGenerator = ‘Use original filename’, slice names are derived from metadata.sliceName when available.

USAGE EXAMPLES

%% 1. Direct saver use
saver = io.SaverFactory.create('Portable Network Graphics (``*.png``)');

opts.Format            = 'Portable Network Graphics (``*.png``)';
opts.showWaitbar       = false;
opts.silent            = true;
opts.overwrite         = true;
opts.FilenameGenerator = 'Use sequential filename';

meta.filename     = 'source.tif';
meta.colorType    = 'grayscale';
meta.lutColors    = [1 1 1];
meta.dataClass    = 'uint8';
meta.maxInt       = 255;
meta.sliceName    = {};
meta.xResolution  = 72;
meta.yResolution  = 72;
meta.imageDescription = 'EM dataset';

data = uint8(rand(256,256,10,1,1)*255);  % [H W D C T]
fnOut = saver.save(data, meta, '/output/slice.png', opts);
% Generates /output/slice_01.png … /output/slice_10.png

%% 2. Via MibDataset (intermediate layer)
opts.Format            = 'Portable Network Graphics (``*.png``)';
opts.showWaitbar       = false;
opts.silent            = true;
opts.overwrite         = true;
fnOut = dataset.save('image', '/output/slice.png', opts);

%% 3. Save mask as PNG sequence
opts.Format            = 'PNG format (``*.png``)';
opts.showWaitbar       = false;
opts.silent            = true;
opts.overwrite         = true;
fnOut = dataset.save('mask', '/output/Mask_slice.png', opts);

SEE ALSO io.SaverFactory, io.savers.BaseSaver, io.savers.TiffSaver, core.MibImage.save, core.MibDataset.save

Constructor Summary
PngSaver(options)

PNGSAVER - Constructor for PngSaver class.

Syntax:
saver = io.savers.PngSaver(options)
Input Arguments:

  • options - (optional) struct, saver-level options (usually empty; per-save options are passed to save() instead)

Output Arguments:

  • obj - instance of the PngSaver class

Method Summary
getSupportedFormats(~)

GETSUPPORTEDFORMATS - Return format strings handled by PngSaver.

Syntax:
formats = obj.getSupportedFormats()
Input Arguments:

(none)

Output Arguments:

  • formats - cell array of format strings for PNG output

save(data, metadata, filename, options)

SAVE - Write a PNG 2-D sequence (one file per Z-slice × time point).

Syntax:
fnOut = obj.save(data, metadata, filename, options)

PNG stores one 2-D image per Z-slice and optionally per time point. The stem of the output filename is used as the base for sequential numbering.

Input Arguments:

  • data - [H, W, D, C, T] numeric array

  • metadata - struct with fields:

    • colorType - 'grayscale' | 'multichannel' | 'indexed'

    • lutColors - (optional) [N × 3] colormap for indexed images

    • colormap - (optional) [N × 3] colormap (alternative to lutColors)

    • sliceName - (optional) per-slice source filenames (for ‘Use original filename’ mode)

    • imageDescription - (optional) [char] comment/description string for PNG files

    • xResolution - (optional) [numeric] X resolution in pixels/unit; default: 72

    • yResolution - (optional) [numeric] Y resolution in pixels/unit; default: 72

  • filename - [char] full path template, e.g. '/out/slice.png'; stem is used as base for sequential names

  • options - struct with fields:

    • Format - format string

    • showWaitbar - logical; default: true

    • silent - logical, suppress dialogs; default: false

    • overwrite - logical; default: true

    • FilenameGenerator - 'Use original filename' | 'Use sequential filename'

Output Arguments:

  • fnOut - cell of char [{nD × nT} × 1] with all saved paths, or single char when only one slice was saved

Example - see class-level documentation above.

PNG is inherently per-slice, so save is a thin wrapper over the streaming primitive saveStream (single code path).

saveStream(provider, metadata, filename, options)

SAVESTREAM - Write a PNG 2-D sequence one slice at a time from a SliceProvider.

Memory-bounded twin of save: pulls each Z-slice (per time point) from provider.getSlice(z, t) and writes it as an individual PNG. See io.savers.BaseSaver.saveStream.

Example - stream a level to a numbered PNG sequence:

provider = io.savers.MibImageSliceProvider(img, 'image', 2, [], numZ, 1, zScale);
saver    = io.savers.PngSaver(struct());
meta.colorType = 'grayscale';
saver.saveStream(provider, meta, 'C:\out\slice.png', ...
    struct('silent',true,'showWaitbar',false,'FilenameGenerator','Use sequential filename'));
% → C:\out\slice_001.png … slice_NNN.png