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5. File related Dialogs |  |
| 5.5. Export File Formats | ||
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5. File related Dialogs | |
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.
![[주의]](images/warning.png)
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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. |
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.
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.
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.
You can set how many times the animation will repeat before it stops. This value is ignored if Loop forever is checked.
When this option is checked, the animation will play repeatedly until you stop it.
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 Layers dialog. Note that some operating systems and applications may override with a lower frame rate due to computer speed, performance, or other technical limitations.
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.
The Delay between frames when unspecified value will be used for all frames.
The Frame disposal when unspecified value will be used for all frames.
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.
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.
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.
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.
Determines if the pixel data should be stored using 8 bits, 10 bits, or 12 bits per color channel.
The tradeoff between speed and compression. Slow will provide a smaller filesize but takes longer to encode.
If checked, the color profile is embedded in the exported image.
If checked, the Exif metadata is embedded in the exported image.
If checked, the XMP metadata is embedded in the exported image.
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.
JPEG 알고리즘은 굉장히 복잡합니다. 또한 이 메뉴얼에서는 다 설명할 수 없을 정도로 많은 옵션들을 가지고 있습니다. 따라서 JPEG 전문가가 아니라면 화질 값을 조절하는 것 정도만 알아도 될 것입니다.
JPEG 포맷으로 저장을 하면, 0 에서 100 까지의 압축률을 조절할 수 있는 대화 상자가 열립니다. 95 이상은 잘 안 쓰이고, 기본값은 85 로 가장 좋은 결과를 보여주지만, 많은 경우 그보다 이하의 값에서도 큰 화질 저하없이 저장이 가능합니다. JPEG 대화 상자의 이미지 창에 미리보기 보여주기 를 이용하면 값에 따른 화질을 미리 확인해 볼 수 있습니다. 이는 JPEG 의 각 옵션값에 따른 변화를 바로바로 보여주지만 이미지 자체를 변형시키지는 않습니다. 따라서 JPEG 대화 상자를 닫으면 원래의 이미지로 돌아갑니다.
![[참고]](images/note.png)
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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. |
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.
이미지를 조금만 변형한 경우, 이 옵션을 사용하면 원본 이미지와 거의 동일한 화질과 크기로 저장할 수 있습니다. 이 옵션은 양자화 단계를 통해 다른 화질 설정을 사용할 때보다 이미지의 손실이 적게 만듭니다.
원본 이미지 파일에서 불러온 화질 설정이 기본값보다 나쁜 경우 “원본 이미지의 화질 설정값 사용” 옵션을 사용할 수 없습니다. 이는 항상 기본값보다 높은 화질을 얻을 수 있도록 하는 안전장치입니다.
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.)
고급 설정에 관한 정보:
JPG compression creates artifacts. By using this option, you can smooth the image when saving, reducing them. But your image becomes somewhat blurred.
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).
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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). |
Whether to export using a CMYK Color Profile.
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.
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.
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.
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).
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 는 “이산 코사인 변환(discrete cosine transform)” 의 약자이며 공간 영역을 주파수 영역으로 옮기는 JPEG 알고리즘의 첫번째 과정입니다. “부동형(float)”, “정수형(integer)”(기본값), “빠른 정수형(fast integer)” 등의 옵션이 있습니다.
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.
정수형 (기본값) : 이 방식은 “부동형” 보다 빠르나, 정확도는 떨어집니다.
fast integer: The fast integer method is much less accurate than the other two.
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.
If the image you loaded has Exif, XMP, IPTC metadata, select which metadata you want to preserve keep when exporting.
You can also save the color profile, a custom comment to be shown in the Image Properties, and include a small preview thumbnail of the image when exporting.
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.
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.
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.
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.
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.
If your image has many transparency levels, the Internet browsers that recognize only two levels, will use the background color of your Toolbox instead.
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 the image resolution, in ppi (pixels per inch).
Date the file was saved.
이미지 정보창을 통해 이 설명을 볼 수 있습니다.
If the image you loaded has Exif, XMP, IPTC metadata, select which metadata you want to preserve keep when exporting.
You can also save the color profile, a custom comment to be shown in the Image Properties, and include a small preview thumbnail of the image when exporting.
Click to save the current settings. Later, you can use to load the saved settings.
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The PNG format supports indexed images. Using fewer colors, therefore, results in a smaller file; this is especially useful for creating web images; see 6.6절. “Indexed mode”. 컴퓨터는 8 bit로 이루어진 “Byte” 를 기본 단위로 동작합니다. 1 byte는 256 색을 지원하는데, 최소 1 byte 이상이 사용되기 때문에 색상수를 256 개 이하로 줄여도 파일 크기를 줄이는데에는 큰 도움이 되지 않습니다. 그리고 “PNG8” 포맷은 GIF 와 마찬가지로 투명도 여부만 가리도록 투명도에 1 bit 만 사용합니다. |
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.
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These two compression modes can only be selected, if the image is in indexed mode and reduced to two colors. Use → → to convert the image to indexed mode. Make sure that “Use black and white (1-bit) palette” is checked. |
You can save layers when exporting to TIFF. Each layer will be a separate page in the TIFF image.
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.
When this is enabled the color values are saved even if the pixels are completely transparent.
Whether to export using a CMYK Color Profile.
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.
When this option is enabled existing EXIF metadata will be saved in the exported TIFF image.
When this option is enabled existing IPTC metadata will be saved in the exported TIFF image.
When this option is enabled existing XMP metadata will be saved in the exported TIFF image.
When this option is enabled the color profile will be saved in the exported TIFF image.
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.
When this option is enabled GeoTIFF metadata that was present in the original image will be saved in the exported TIFF image.
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.
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.
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.
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.
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.
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.
When this option is enabled existing EXIF metadata will be saved in the exported image.
When this option is enabled existing IPTC metadata will be saved in the exported image.
When this option is enabled existing XMP metadata will be saved in the exported image.
When this option is enabled the color profile will be saved in the exported image.
When this option is enabled a thumbnail will be saved in the exported image.
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.
