jAlbum / Settings / Images

This section controls how images are generated

General

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Sets image quality and size limits for thumbnail and slide images.

Scaling method

There algorithms for scaling images are Fast, Medium and Smooth. They affect how your original images get reduced, when linking to scaled-down images, in size to meet the image bounds. The settings are a trade off between speed and creating processing artefacts, depending on the image being sampled. Advantages of each method tends to be that they preserve a specific property, like hard edges. Disadvantages are the generation of artefacts such as blocking, ringing, moire and blurring. If the images generated suffer from artefacts try another scaling method.

Fast uses nearest neighbor interpolation but can result in ‘jagged results’.

Smooth is the slowest, but will give the best result. It uses an ‘area averaging’ algorithm, or if using hardware acceleration (Settings/Images/Advanced) bilinear interpolation.

Smooth, the default setting, is recommended by jAlbum. It is very similar to Medium in quality but operates slower. If you use Medium but your images are high contrast and you are not happy with the scaled images then switch to smooth.

With smooth selected, you have access to four additional variations.

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Blackman-Bessel, Blackman-Sinc, Lanczos and Mitchell. These are all variations of the standard method and give greater scope for getting the best possible scaled image.


Sharpen

Sets the amount of sharpening to be applied to scaled-down images. If you are using images that are already within the image bounds then sharpening should be set to a low value. The default setting is 25.

JPEG quality

This affects the image quality and file size. A low value will result in smaller file sizes but may suffer from ‘jpeg artifacts’. A value too high will not result in a significant improvement in quality, but will result in much bigger files. The default setting is 85.

Thumbnails bounds

Sets the limits for thumbnail images, width x height in pixels. Images will be scaled so that neither the width nor height exceeds the set limits.

Images bounds

Sets the limits for scaled-down images, width x height in pixels. Images will be scaled so that neither the width nor height exceeds the set limits. This field is disabled if ‘Settings/Pages/Image linking from thumbnails’ is set to Link to originals.

The bounds fields allows you to enter custom bounds too! jAlbum will never distort the width/height ratio of your images. This means that you can safely use bounds like 1000x1000 to ensure that neither the width or height goes above 1000. A ratio like 10000x800 is commonly used to allow a mix of panoramic images and ordinary images having the same height.


HiDPI thumbnails & Images

When checked the images will be scaled to twice the size set by the image bounds, providing the original is big enough, but the album will display images as set by the image bounds. This is to support displays that have a higher pixel density than standard, for example 326 pixels per inch instead of 72ppi.

Note, if the original image is not large enough to support the HiDPI slide image size then a small yellow warning triangle will appear at the top right of the thumbnail image. There is currently no warning for thumbnail images not being big enough to generate a HiDPI thumbnail.


Copyright embedding

You can embed XMP metadata to the generated slide images in your album, you can add creator, copyright and a copyright URL. For this to take effect you also need to ensure Settings/Advanced/Metadata/ Include xmp metadata in generated images is checked. The metadata tags added are of the form:

Creator » xmp.dc:creator[1]
Copyright » xmp.dc:rights[1]
Copyright URL » xmp.xmpRights:WebStatement

If the information entered is changed for any reason you will need to perform a 'Make all' operation in order for the updated metadata to be applied. If you select 'overwrite existing it will replace the metadata rather than appending it.

Advanced

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Advanced Settings controls how images are created.

Force processing of small images

Normally, if a source image is smaller than the slide image bounds, and no filters are being applied, jAlbum will copy the source file to the album but with this enabled it will process those images instead. This may be useful if your source images have lots of non repeating detail, and their file sizes are high as a result, as processing them may reduce the file size.

After enabling this to reprocess existing images you must either:

Perform a 'Make All';
Have Preferences/Album/Synchronise output directory enabled and then exclude, re-include and 'Make album'.


Force JPEG

If selected, thumbnail and/or slide images, supported image formats will be converted to JPEG format in the album. Note, GIF images are normally converted to PNG format but change to JPEG with this option selected.


Disable colour subsampling

When checked and compression quality is set to 90% or more it will produce even better looking JPEGs. Disabling chroma/colour subsampling doubles the horizontal and vertical colour resolution of images, however it increases the image file size by about 17%. See this article by Rick Matthews, prefessor of physics at Wake Forest University, North Carolina.

You will need to perform a ‘Make all’ after toggling the ‘Disable colour subsampling’ status to have images reprocessed. To only have thumbnails without colour subsampling, tick ‘Disable colour subsampling’ AND ‘Save thumbnails with high JPEG compression quality.’

Note, images must be larger than the image bounds in general settings above.

Attempt to use hardware accelerated scaling

Will try to use graphic processors to speed up image processing. Image quality may be affected with certain graphic cards.


Superimpose play icon onto video thumbnails

If selected the ubiquitous 'play' icon, of a triangle within a circle, is superimposed on video thumbnails. Note, some skins may override this setting and apply their own custom filmstrip regardless of the setting. If the project settings was saved with this off and you turn it on and after a ‘Make album’ the overlay does not appear then a ‘Make all’ will be needed to force a rebuild of all images.


Background color for transparent images

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If force jpeg writing (above) is enabled then images with transparent backgrounds will have a background color as set here. You can open up a color picker window, see figure to the left, by double clicking on the small square just before the color value field.