Scanner's dither settings. 0x0500 ∙ 1280
IG_ISIS_TAG_DITHER sets or reads the dither settings of a scanner.
IG_ISIS_TAG_TYPE_STRING
All scanner drivers.
The application must get choices (using IG_ISIS_choice_get_ascii) to be aware of the number of values and the actual values of IG_ISIS_TAG_DITHER. Note that the first choice for this tag actually represents no dithering and is usually called "None." The actual values are defined within the scanner itself, and have names such as "A -- 8x8 w/53 grays," and "4x4 Diagonal." Scanners that support dithering store the IG_ISIS_TAG_DITHER values in an array. The lpwCount parameter of the IG_ISIS_choice_get_count function returns the number of dither choices for IG_ISIS_TAG_DITHER. The lpwLength parameter of the IG_ISIS_choice_get_ascii Length function returns the number of characters in each IG_ISIS_TAG_DITHER choice.
Many scanners only support dithering of binary images, and so the following tags may affect whether IG_ISIS_TAG_DITHER reports values other than `None.' Furthermore, some scanners may return different choices for IG_ISIS_TAG_DITHER depending on the values of the color format tags.
IG_ISIS_TAG_SAMPLESPERPIXEL ∙ IG_ISIS_TAG_BITSPERSAMPLE ∙ IG_ISIS_TAG_PHOTOMETRICINTERPRETATION ∙ IG_ISIS_TAG_DITHER
Because dither patterns are unique to each scanner, there is no way to reduce the choices to numbers that can be understood programmatically. Your application must get the ASCII values of each of the IG_ISIS_TAG_DITHER choices, present them to the user, let the user make a selection, and then set the desired choice by setting the ASCII value.
IG_ISIS_TAG_PHOTOMETRICINTERPRETATION