The two most important factors in image file formats that affect their ability to support gigabyte-sized images are as follows:
- Maximum allowed image dimensions. This usually depends on the integer format used for storing image dimensions.
- File size limitation. This usually depends on the integer format used for storing lengths or offsets to various data in the file. If a file is stored compressed, image size after decompression may be greater than the maximum supported file size.
- Some file formats have limitations on blocks (chunks, strips) of pixel data, but allow multiple such blocks to exist in a file, and thus avoid the limitation on the file size.
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Although some file formats allow storing gigabyte-sized images, particular software may have difficulties with reading or writing them. |
The table below lists some of the popular file formats and their capabilities for storing gigabyte-sized images.
|
Image Format |
Max Available Image Dimensions (width x height, pixels) |
Max Image Size, When Uncompressed, Approximately (for a 24-bit RGB image) |
File Size Limit, Approximately |
|
JPEG, EXIF JPEG |
65535 x 65535
|
12 Gb |
None |
|
TIFF, EXIF TIFF |
2^32-1 x 2^32-1 |
3 * 2^24 Tb |
4 Gb 1 |
|
JP2,JPX |
2^32-1 x 2^32-1 |
3 * 2^24 Tb |
None |
|
PSB |
300 000 x 300 000 |
250Gb |
None |
|
PSD |
30 000 x 30 000 |
2,5Gb |
4 Gb |
|
BMP |
2^31-1x 2^31-1 |
3 * 2^20Tb |
4 Gb |
|
PNG |
2^32-1 x 2^32 - 1 |
3* 2^24Tb |
None |
|
DICOM |
65535 x 65535
|
12 Gb |
2 Gb |
|
PBM / PGM / PPM / PNM |
None |
None |
None |
|
TGA |
65535 x 65535 |
12 Gb |
4 Gb |
1 TIFF format uses 32-bit unsigned integers to store data offsets and sizes. As a result, a strip of pixel data in a TIFF image cannot be stored at an offset greater than 4 Gb, and its size formally cannot be greater than 4 Gb. Thus, the size of the largest compliant TIFF image can be a bit less than 8 Gb. This assumes that two strips of nearly 4 Gb size are used.
ImageGear supports the reading and writing of single-page, single-strip, single-tiled uncompressed TIFF images where strip byte counts are greater than 4 Gb. If the size of a strip exceeds 4 Gb, ImageGear writes 0 to the StripBytes tag. The reader can calculate strip size from image dimensions in such a case.
Note, though, that such files are formally incompliant and may not be supported by other readers.When writing a gigabyte-sized TIFF image, make sure to keep the “IMAGE_BEFORE_IFD” TIFF control parameter set to its default value of FALSE.