### 5.41. Export Image as PNG

#### 5.41.1. Visão geral

Figura 15.85. The PNG Export dialog

| Nota
The PNG format supports indexed images. Using fewer colors, therefore, results in a smaller file; this is especially useful for creating web images; see Secção 6.6, “Indexed mode”. Computers work on 8 bits blocks named “Byte”. A byte allows 256 colors. Reducing the number of colors below 256 is not useful: a byte will be used anyway and the file size will not be less. More, this “PNG8” format, like GIF, uses only one bit for transparency; only two transparency levels are possible, transparent or opaque.

#### 5.41.2. Options

Pixel format

  By default your PNG image is exported in a pixelformat that resembles the settings of your image in GIMP. This is usually what you want, but when you need a specific output format you can change this here to 8 or 16 bits per channel RGB or Grayscale, with or without alpha channel.

Compression level

  Since compression is not lossy, the only reason to use a compression level less than 9, is if it takes too long to compress a file on a slow computer. Nothing to fear from decompression: it is as quick whatever the compression level.

Interlacing

  Checking interlace allows an image on a web page to be progressively displayed as it is downloaded. Progressive image display is useful with slow connection speeds, because you can stop an image that is of no interest; interlace is of less use today with our faster connection speeds.

Save color values from transparent pixels

  When this option is checked, the color values are saved even if the pixels are completely transparent. But this is possible only with a single layer, not with a merged composition. When a multi-layer image gets exported to a single-layer file format, there is no way GIMP could preserve the color values in the transparent pixels.

Metadata (edit)

  You can click the “(edit)” link to open the metadata editor to change or add any metadata that you want to be included in the image. Note: you will also still need to enable the relevant metadata saving options listed below.

  The metadata settings in the export dialog override the default values set in your Metadata Export Preferences.

Save Exif data

  When this option is enabled, EXIF metadata will be saved in the exported image.

Save IPTC data

  When this option is enabled, IPTC metadata will be saved in the exported image.

Save XMP data

  When this option is enabled, XMP metadata will be saved in the exported image.

Save color profile

  When this option is enabled, the color profile will be saved in the exported image.

Save thumbnail

  When this option is enabled a thumbnail will be saved in the exported image as part of the EXIF metadata. This will also cause certain EXIF tags to be saved, even if you have disabled saving EXIF metadata.

Save background color

  If your image has many transparency levels, the Internet browsers that recognize only two levels, will use the background color of your Toolbox instead.

Save layer offset

  PNG supports an offset value called the “oFFs chunk”, which provides position data. Unfortunately, PNG offset support in GIMP is broken, or at least is not compatible with other applications, and has been for a long time. Do not enable offsets, let GIMP flatten the layers before saving, and you will have no problems.

Save resolution

  Save the image resolution, in ppi (pixels per inch).

Save creation time

  Date the file was saved.

Save comment

  You can read this comment in the Image Properties.

Save Settings

  Click to save the current settings. Later, you can use Load Saved Settings to load the saved settings.

5.40. Export Image as Alias Pix |  | 5.42. Export Image as PNM, PAM, PBM, PGM, PPM

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