8 bpc( bit per channel) images can be saved as BMP with different bit depths,
as well with 16 bpp (bit per pixel).
In the Advanced settings is a choice of
X1 R5 G5 B5
R5 G6 B5
X4 R4 G4 B4
X1 and X4 are channels with arbitray meaning (undefined alpha channels).
These modes are still available in PS CS6
Best regards --Gernot Hoffmann
As far as I remember BMP 16bpp does not work with color tables (like indexed color).
For instance R5 G6 B5 is directly derived from R8 G8 B8 by binary shifting and rounding.
8bit color depth is 24bit for each pixel color and 16bit color depth is 48bit foe each pixels color. If you change from 8bit to 16bit you do not gain any color information unless you have the information like in camera raw data. However you will be able to edit with more latitude in 16bit color mode. However if you want to save some image file formats do not support 16bit color depth. For a Jpeg save Photoshop will converted to 8bit color depth if the document is a 16bit color document. BMP will not be a save option unless you change the documents mode to 8bit color. PNG and Tiff doe support 16bit color.
A bitmap document is strange its 1 bit color you will notice all other options grayed out. You can not even place in other images.
I have some bitmaps, where I would like to change the colortable from 24 bit colors to 16 bit colors.
A while ago we talked about 4 bit per pixel, now we are talking about 16 bit per pixel. The mentioned BMP
formats were long ago used for games.
Best regards --Gernot Hoffmann
Thank you for all the answers
I have to make bitmaps for our software department. The software has to be implemented in 16-bit color resistive touch screens.
To save space they want me to make colortables with only 16-bit colors.
Do you know where to download Photoshop CS6 ?
I think your confusing different things. On one side Digital Image editing procing. On an other side Digital Image file formats. On an other side Touch Screen technology. The Touch screen color technology basically has little to do with any aspect of image editing. Its function is that of a display device that has limited input support in CC 2014 touch support.
The reality is your most likely need to produce Image files in some file format that you employer can use to promote their offering.
At my job, we use bitmaps in the resistive displays. Generated from Photoshop.
The only thing, that I would like to do, is to make pictures with 16 bit colortables.
Maybe it is not possible in Photoshop to make colourtables/Schwatches with only 16 bit dept ?
With this I mean on the picture below, that it is not possible to go op to 255,255,255 (24 bit colours), but only 16,16,35 (16 bit colours).
Let us consider the possibilities of the file format Windows Bitmap BMP. Photoshop can save
as BMP with different color depths, but this has nothing to do with "Photoshop Bitmap".
Mode Indexed color (BMP, 8 bit per pixel) uses a color look-up table, a CLUT:
256 rows with 3 bytes for R, G and B (one byte each).
The image contains for each pixel one byte, which is a pointer to the CLUT, from where the
color bytes are taken. Finally we have a 24 bit per pixel color representation (True color).
For GIF it's almost the same, but one row in the CLUT means transparency.
Building the CLUT for an image which may contain originally 256^3 diffent colors is called
Color quantization (a key word for a further search).
If the display should require a smaller number of bits, e.g. 5R, 6G, 5B (green is more accurate),
then the CLUT can be taken from the Indexed color BMP image and modified:
R: Shift right 3 bits and round
G: Shift right 2 bits and round
B: Shift right 3 bits and round
Assemble R,G,B in one word with 16 bit.
Similarly, if the display should require 5R, 5G, 5B.
Such a table cannot be generated directly by Photoshop.
Mode High color (BMP, 16 bit per pixel) does not use a CLUT. Perhaps, at the time when these
file formats were developed, a CLUT with 2^16 rows was considered as nonsensical.
Photoshop can generate a BMP image with 16 bit per pixel by one of three modes, as explained
earlier in my previous post.
Thus it is possible to convert an image, which contains an arbitrary number of "swatches"
as defined by True Color 24 bit per pixel, into High color 16 bit per pixel by Photoshop. From the
result one can take the coding and build a table.
Arbitrary means: up to the maximal number, e.g. 32*64*32 swatches for 5R 6G 5B.
The further proceeding depends strongly on the decision only 256 colors / more colors.
Accepting the 16 bit per pixel limit, one may use a fixed full size CLUT and an automatic conversion
True Color – High Color with Dithering.
Best regards --Gernot Hoffmann
Thanks for all the feedback.
Does anyone know if there is a program somewhere, which has the ability to work with a 16 bit CLUT?
I need to create a 16 bit BMP image for a multimedia device.
By this I mean a 16 bit file NOT 16 bit per channel.
The file has a diagonal colored gradient.
When the image is created as an RGB 8 bits per channel and saved as a 16 bit bmp file the gradient is horribly banded.
If I make the image "indexed color" I can only save it as an 8 bit file. The 8 bit file with 255 colors looks fine BUT the device will not accept it as it is not 16 bit bmp.
Is it possible to create a 16 bit bmp file with indexed color?
..... and of course HOW?
I am using CS4.
When you change your image to "Indexed colour", you have to choose the "Local (Selective)" option having 256 colours.
Then it is possible to save the image at a bmp. with 4 bit color depth. (4 bit = 2*2*2*2 = 16 bit image)
I am using Photoshop CC 2014.2.2 Release.
It should be possible in CS4 I would mean.
Thanks for you help.
The results of my experiments are attached:
Top left original 8 bit per channel project file.
Top right default saving as a 16 bit file (1555)
Row 2 left red 255 black gradient saved as 565
Row 2 right green 255 black gradient saved as 565
------ you can see the different one bit makes with the green
Row 3 left blue 255 black gradient saved 565
Row 3 right green 255 black gradient saved 1555.
That is because your eye is least sensitive to blue and changes in value blue.
(removed extra info on vision that might get too confusing)