5.5. Export File Formats
| 5. File related Dialogs |

### 5.5. Export File Formats

When exporting an image, most file formats have additional options that can be set. If that is the case, then a new dialog will open after you have selected the filename and export file format. This section will document the dialogs for all export file formats.

#### 5.5.1. Export Image as GIF

Figure 15.76. The GIF Export dialog

| Warning
The GIF file format does not support some basic image properties such as print resolution. If you care for these properties, use a different file format like PNG.

GIF Options
  Interlace

    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 comment

    GIF comments support only 7-bit ASCII characters. If you use a character outside the 7-bit ASCII set, GIMP will export the image without a comment, and then inform you that the comment was not saved.

Animated GIF Options
  As animation

    When this option is checked, the image will be exported as an animation. Note that this option will be disabled (and the animation options will not be visible) if the image has only one layer.

  Number of repeats

    You can set how many times the animation will repeat before it stops. This value is ignored if Loop forever is checked.

  Loop forever

    When this option is checked, the animation will play repeatedly until you stop it.

  Delay between frames when unspecified

    You can set the delay, in milliseconds, between frames if it has not been set before. In this case, you can modify every delay in the Layer Dialog. Note that some operating systems and applications may override with a lower frame rate due to computer speed, performance, or other technical limitations.

  Frame disposal when unspecified

    If this has not been set before, you can set how frames will be superimposed. You can select among three options:

    - I don't care: you can use this option if all your layers are opaque. Layers will overwrite what is beneath.

    - Cumulative layers (combine): previous frames will not be deleted when a new one is displayed.

    - One frame per layer (replace): previous frames will be deleted before displaying a new frame.

  Use delay entered above for all frames

    The Delay between frames when unspecified value will be used for all frames.

  Use disposal entered above for all frames

    The Frame disposal when unspecified value will be used for all frames.

#### 5.5.2. Export Image as HEIF/HEIC

HEIF stands for High Efficiency Image File Format. Also known as HEIC High Efficiency Image Coding.

Twice as much information can be stored in a HEIF image as in a JPEG image of the same size, resulting in a better quality. As of September 2022, no browser supports HEIF natively.

More information in Wikipedia.

Figure 15.77. The HEIF/HEIC Export dialog

HEIF Options
  Lossless

    When checked, the image will be exported with lossless compression. This will create a higher quality image at the cost of a larger file size.

  Quality

    If Lossless is not checked, this value determines the quality of the image compression. 100 provides the best quality image and lowest compression, while 0 provides the highest compression and worst quality image.

  Pixel format

    Defines what pixel format the exported image should use for color sub-sampling. There are three options:

    - YUV420: Suitable for photographs with lossy compression. This format is most compatible with other software that uses HEIF.

    - YUV444: When used with a high Quality setting, this format exports a visually lossless image.

    - RGB: Useful when exporting images with true lossless quality.

  Bit depth

    Determines if the pixel data should be stored using 8 bits, 10 bits, or 12 bits per color channel.

  Save color profile

    If checked, the color profile is embedded in the exported image.

  Save Exif

    If checked, the Exif metadata is embedded in the exported image.

  Save XMP

    If checked, the XMP metadata is embedded in the exported image.

#### 5.5.3. Export Image as JPEG

JPEG files usually have an extension .jpg, .JPG, or .jpeg. It is a very widely used format, because it compresses images very efficiently, while minimizing the loss of image quality. No other format comes close to achieving the same level of compression. It does not, however, support transparency or multiple layers.

Figure 15.78. The JPEG Export dialog

The JPEG algorithm is quite complex, and involves a bewildering number of options, whose meaning is beyond the scope of this documentation. Unless you are a JPEG expert, the Quality parameter is probably the only one you will need to adjust.

Quality

  When you save a file in JPEG format, a dialog is displayed that allows you to set the Quality level, which ranges from 0 to 100. Values above 95 are generally not useful, though. The default quality of 85 usually produces excellent results, but in many cases it is possible to set the quality substantially lower without noticeably degrading the image. You can test the effect of different quality settings by checking Show Preview in image window in the JPEG dialog.

  | Note
  Please note, that the numbers for the JPEG quality level have a different meaning in different applications. Saving with a quality level of 80 in GIMP is not necessarily comparable with saving with a quality level of 80 in a different application.

Use quality settings from original image

  If a particular quality setting (or “quantization table”) was attached to the image when it was loaded, then this option allows you to use them instead of the standard ones.

  If you have only made a few changes to the image, then re-using the same quality setting will give you almost the same quality and file size as the original image. This will minimize the losses caused by the quantization step, compared to what would happen if you used different quality setting.

  If the quality setting found in the original file are not better than your default quality settings, then the option “Use quality settings from original image” will be available but not enabled. This ensures that you always get at least the minimum quality specified in your defaults. If you did not make major changes to the image and you want to save it using the same quality as the original, then you can do it by enabling this option.

Show preview in image window

  Checking this option causes each change in quality (or any other JPEG parameter) to be shown in the image display. (This does not alter the image: the image reverts back to its original state when the JPEG dialog is closed.)

Keep metadata

  If the image you loaded has Exif, XMP, IPTC metadata, they are preserved, and you can keep them or not when exporting to JPEG.

Save thumbnail, Save color profile

  Many applications use the small thumbnail image as a quickly available small preview image.

Comment

  You can edit the comment attached to the image you loaded or write a new one.

Advanced Options

  Some information about the advanced settings:

  Optimize

    If you enable this option, the optimization of entropy encoding parameters will be used. The result is typically a smaller file, but it takes more time to generate.

  Smoothing

    JPG compression creates artifacts. By using this option, you can smooth the image when saving, reducing them. But your image becomes somewhat blurred.

  Use arithmetic coding

    Arithmetic encoding is a form of entropy encoding (a lossless data compression scheme) that can be used in exporting as JPEG. Images using arithmetic encoding can be 5 - 10 % smaller. But older software may have trouble opening these images.

  Use restart markers

    The image file can include markers which allow the image to be loaded as segments. If a connection is broken while loading the image in a web page, loading can resume from the next marker.

  Interval (MCU rows)

    JPEG images are stored as a series of compressed square tiles named MCU (Minimum Coding Unit). You can set the size of these tiles (in pixels).

  Progressive

    With this option enabled, the image chunks are stored in the file in an order that allows progressive image refinement during a slow connection web download. The progressive option for JPG has the same purpose as the interlace option for GIF. Unfortunately, the progressive option produces slightly larger JPG files (than without the progressive option).

    | Note
    Beware that certain older TVs and photo frames (and maybe other devices) may not be able to show jpeg images that have been exported with the progressive setting enabled (which is the default).

  Subsampling

    The human eye is not sensitive in the same way over the entire color spectrum. The compression can use this to treat slightly different colors that the eye perceives as very close, as identical colors. Three methods are available:

    - 1x1,1x1,1x1 (best quality): Commonly referred to as (4:4:4), this produces the best quality, preserving borders and contrasting colors, but compression is less.

    - 2x1,1x1,1x1 (4:2:2): This is the standard subsampling, which usually provides a good ratio between image quality and file size. There are situations, however, in which using no subsampling (4:4:4) provides a noticeable increase in the image quality; for example, when the image contains fine details such as text over a uniform background, or images with almost-flat colors.

    - 1x2,1x1,1x1 This is similar to (2x1,1x1,1x1), but the chroma sampling is in the horizontal direction rather than the vertical direction; as if someone rotated an image.

    - 2x2,1x1,1x1 (smallest file): Commonly referred to as (4:1:1), this produces the smallest files. This suits images with weak borders but tends to denature colors.

  DCT Method

    DCT is “discrete cosine transform”, and it is the first step in the JPEG algorithm going from the spatial to the frequency domain. The choices are “float”, “integer” (the default), and “fast integer”.

    - float: The float method is very slightly more accurate than the integer method, but is much slower unless your machine has very fast floating-point hardware. Also note that the results of the floating-point method may vary slightly across machines, while the integer methods should give the same results everywhere.

    - integer (the default): This method is faster than “float”, but not as accurate.

    - fast integer: The fast integer method is much less accurate than the other two.

#### 5.5.4. Export Image as PNG

Figure 15.79. The “Export Image as PNG” dialog

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 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 gamma

  Gamma correction is the ability to correct for differences in how computers interpret color values. This saves gamma information in the PNG that reflects the current Gamma factor for your display. Viewers on other computers can then compensate to ensure that the image is not too dark or too bright.

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 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.

Pixelformat

  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.

Keep metadata

  If the image you loaded has Exif, XMP, IPTC metadata, they are preserved, and you can keep them or not when exporting to PNG.

Save Defaults

  Click to save the current settings. Latter, you can use Load Defaults to load the saved settings.

| Note
The PNG format supports indexed images. Using fewer colors, therefore, results in a smaller file; this is especially useful for creating web images; see Section 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.

#### 5.5.5. Export Image as TIFF

Figure 15.80. The TIFF Export dialog

Compression

  This option allows you to specify the algorithm used to compress the image.

  - None: is fast, and lossless, but the resulting file can be very large.

  - LZW: The image is compressed using the “Lempel-Ziv-Welch” algorithm, a lossless compression technique. This is efficient and fast. More information at [WKPD-LZW].

  - Pack Bits: is a fast, simple compression scheme for run-length encoding of data. Apple introduced the PackBits format with the release of MacPaint on the Macintosh computer. A PackBits data stream consists of packets of one byte of header followed by data. (Source: [WKPD-PACKBITS])

  - Deflate: is a lossless data compression algorithm that uses a combination of the LZ77 algorithm and Huffman coding. It is also used in Zip and Gzip files and PNG images. Source: [WKPD-DEFLATE].

  - JPEG: is a very good compression algorithm but lossy. This is the same compression as used in JPEG images. Since it is lossy, you should not use this when image quality is important. This compression can not be used when your image is in indexed mode.

  - CCITT Group 3 fax and CCITT Group 4 fax are black and white formats developed to transfer images by FAX.

    | Note
    These two compression modes can only be selected, if the image is in indexed mode and reduced to two colors. Use Image → Mode → Indexed to convert the image to indexed mode. Make sure that “Use black and white (1-bit) palette” is checked.

Save layers

  Since GIMP-2.10.12, you can save layers when exporting to TIFF. Each layer will be a separate page in the TIFF image.

Crop layers

  When Save layers is checked, this option, which is enabled by default, will resize all layers to the size of the image. TIFF images can not have negative offsets. This option enables you to import the TIFF again without having to change the position of layers that had a different size as the image in the original.

Save color values from transparent pixels

  When this is enabled the color values are saved even if the pixels are completely transparent.

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.

Save Exif data

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

Save IPTC data

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

Save XMP data

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

Save color profile

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

Save thumbnail

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

Save GeoTIFF data

  When this option is enabled GeoTIFF metadata that was present in the original image will be saved in the exported TIFF image.

Save comment

  Here you can enable saving a comment that is associated with the image. The comment can be entered in the text box below this option.

#### 5.5.6. Export Image as WebP

Figure 15.81. The WebP Export dialog

Source Type

  This selects the type of image you are trying to export. Presumably this will help in deciding the best way to compress the image.

  Choices are: Default, Picture for digital pictures, like portraits or inside shots, Photo for outdoor photography with natural lighting, Drawing for hand or line drawing, with high-contrast details, Icon for small-sized colorful images, and Text for images containing mostly text.

Lossless

  When checked, the image will be saved in a way that keeps the original quality. This disables the Image quality and Alpha quality settings. When unchecked, the image will be saved based on the quality settings below, which may cause some loss of quality, but at a better compression ratio. This is the default.

Image quality, Alpha quality

  These settings determine at what quality the image will be saved. A higher image quality usually means a larger filesize. When filesize is important you can check if a lower quality is still good enough for your purposes.

Use Sharp YUV

  When checked, a sharper and more accurate RGB to YUV conversion method is used to export the image. This can better preserve fine details like thin lines in the final image. Setting this option can increase the export time for an image, and it is only available when Lossless is not checked.

Save Exif data

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

Save IPTC data

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

Save XMP data

  When this option is enabled existing 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.

#### 5.5.7. Export Image as MNG

Figure 15.82. Export MNG File Dialog

MNG is acronym for “Multiple-Image Network Graphics”.

No common web browsers recognize the MNG animation format. See https://en.wikipedia.org/wiki/Multiple-image_Network_Graphics.

5.4. Export File |  | 6. Preferences Dialog

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