| From: | Oliver Roberts |
| Date: | 11 Sep 2001 at 00:35:18 |
| Subject: | Re: [amiga-c] DataTypes in 15/16 bits |
On 11-Sep-01 00:01:27 BST, Allan Odgaard wrote:
> On Mon, 10 Sep 2001, Sensei wrote:
>> investigation I have found that datatypes when are loading picture in 16
>> bit
>> (and probably 15 bits too, but I have not checked this case) are
>> creating matrix of very close pixels no matter if the original picture
>> has solid color or not! [...]
> The reason is that the picture.datatype will apply Floyd Steinberg error
> diffusion to 24 bit images shown in a lower colour resolution (as this
> may improve the display of gradients).
>
> You should disable dither and probably this will fix the problem. For the
> P96 picture.datatype this was done using an environment variable, but I'm
> quite sure it can be done through the API for OS 3.5+.
Indeed it can - setting PDTA_DitherQuality to 0 (probably best to do this
at NewDTObject()) will disable 24-bit->15/16-bit dithering.
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