Livingstone's 1871 Field Diary

A Multispectral Critical Edition

Note on Spectral Images
Spectral image processing uses tailored mathematical algorithms in order to manipulate and enhance raw spectral image data. In the case of Livingstone’s manuscripts, such processing relies on the fact that different ink types on a given page (for instance, Livingstone’s ink, the ink of the newsprint, etc.) behave differently under different bands of wavelengths of light. Imaging scientists use this differentiated behavior to create processed images (renderings of combinations of bands) that distinguish among what may be otherwise very subtle differences in color.
Figures 1, 2, 3, 4, 5, 6, 7, 8, 9. Livingstone, 1871 Field Diary, 297c/126, detail. Nine spectral image representations of the same text. Each offers data not available in the others. Top row: color, pack8 (0940), pseudo. Middle row: pca621r, adap_Thresh, pcolor. Bottom row: ratio, sharpie, raking.
The Livingstone team has applied spectral image processing to nearly all the pages of the 1871 Field Diary in order to address the principal challenges posed by Livingstone’s manuscript:
1) the fading of Livingstone’s handwritten text to the point of invisibility in much of the diary, and
2) the additional difficulty in reading Livingstone’s text due to the continuing prominence of the newsprint over which he wrote.
Due to these challenges, the team took as its primary processing objectives, first, suppressing the printed text, and, second, enhancing Livingstone’s handwritten text. Secondary objectives included processing to highlight the topography of select manuscript pages via the raking method (limited to those folia that had not been laminated, see The Manuscript) and using tailored processing methods for manuscript areas particularly difficult to decipher via the “intercept” method. The team also used the raw spectra image data to produce highly accurate color TIFF images of nearly each page of the diary.
The tables below set and define the processed images types available through this critical edition and through the Livingstone Spectral Image Archive. An overview of the processing methods used on Livingstone’s 1871 Field Diary appears in the Project History and Archive section. Additional information on spectral image processing appears in the related section from Livingstone’s Letter from Bambarre.
Color Images
File Suffix Short Name Processing Description
color color Each color image is created using registered, 16-bit flattened TIFF images captured under five visible illuminant bands, 638 nm (red), 592 nm (amber), 535 nm (green), 505 nm (cyan), and 450 nm (royal blue). A set of linear formulae is used to calculate calibrated color values from the five bands at each pixel position, and each image is output using a CIE L*a*b color space.
PCA Image Types
File Suffix Short Name Processing Description
pca321r_pcolor, pca421r_pcolor, pca621r_pcolor, pca721r_pcolor pca_pcolor Pseudocolor image made up of principal component bands with the hue angle rotated.

pca321r, pca421r, pca621r, pca721r, pca321r_1, pca321r_2

pcar Grayscale image that is extracted from a single channel of the corresponding pca###r_pcolor image (note: the ### indicates the principal component bands used).
pca321r_adapThresh adapThresh Adaptive threshold. A bitonal image (black, white) is calculated from a gray-scale image where the gray value used to threshold is based on the local statistics, i.e., it "adapts" to the local situation.
pca321r_adapThresh_multiply, pca321r_1_adapThresh_multiply, pca321r_2_adapThresh_multiply, pca421r_adapThresh_multiply, pca621r_adapThresh_multiply, pca721r_adapThresh_multiply adapThresh_multiply Grayscale image that is the result of the multiplication of the thresholded grayscale image and the corresponding pca###r image (note: the ### indicates the principal component bands used).
Pseudocolor Image Types
File Suffix Short Name Processing Description
0365_packflat8, 0450_packflat8, 0465_packflat8, 0505_packflat8, 0535_packflat8, 0592_packflat8, 0638_packflat8, 0700_packflat8, 0735_packflat8, 0780_packflat8, 0850_packflat8, 0940_packflat8, RABL_packflat8, RABR_packflat8, RAIL_packflat8, RAIR_packflat8 pack8 A linear contrast stretch applied to the 16-bit single-wavelength images. The black and white values were set 3 standard deviations away from the average value. The values beyond 3 standard deviations were clipped to black or white.

intercept

intercept The infrared images (700 nm - 940 nm) were fit to a best straight line on a pixelwise basis. This generates "slope" and "intercept" images.
pseudo_0505-0780 pseudo The 505 nm and 780 nm wavelengths are combined in a no-veil pseudocolor image with the 780 in the red separation and the 505 in the blue and green separations.
pseudo_0780 bleedthrough The505 nm and 780 nm wavelengths from one side are put into the red and green separations, respectively. The 505 nm wavelength image of the reverse side is reversed and aligned with the front side, and placed in the blue separation.
pseudoratio_0505-0780 pseudoratio The 505 nm and 780 nm wavelengths are divided by the 940 nm wavelength and then combined in a standard pseudocolor image.
RAIPratio RAIPratio Left and right raking infrared images are divided by the non-raking 940 nm image and used in a standard pseudocolor image.
raking_irdiff surface The left and right raking images in infrared are differenced, divided by the non-raking 940 nm wavelength, then linearly stretched to fit 6 standard deviations from white to black.
RAPRratio RAPRratio The right raking blue and infrared images are divided by the non-raking 940 nm image and used in a standard pseudocolor image.
RARR RARR The right raking blue image is divided by the right raking infrared image and then linearly contrast stretched.
ratio_by_0940 spectral ratio The 450 nm, 592 nm and 850 nm wavelengths are divided by the 940 nm wavelength, stretched to fit 6 standard deviations from white to black and put into the red, green and blue separations respectively.
RIRL RIRL Left and right raking infrared images are differenced and linearly contrast stretched.
sharpie_0505-0780 sharpie The 505 nm and 780 nm wavelengths are combined in a no-veil pseudocolor image with the 780 in the red separation and the 505 in the blue and green separations. The sharpie image is made by linearly stretching the difference of the red and blue separations of the pseudocolor image.
sharpieratio_0505-0780 sharpieratio The 505 nm and 780 nm wavelengths are divided by the 940 nm wavelength and then combined in a standard pseudocolor image. The sharpie image is made by linearly stretching the difference of the red and blue separations of the pseudocolor image.
XML Practices