For graphics processing I met in Java “ByteProcessor”.
Tell me where I’m wrong.
If I understood correctly this converts a color image to a grayscale image.
I can transform a pixel to gray, so the 3 components R, G, B have the same value.
Can a 24 bit image be transformed into 8 bit in RB? And so will I get a gray image?
Alternatively can I create an array of bytes (0…255) with the value of R, G or B?
Of course, you can convert an image to greyscale in Xojo. Even a quick goggle showed me multiple methods to do greyscale.
Not in ‘one line of code’
You can do it in a loop, setting pixels (slow)
If you have plugins, there are ‘one command’ techniques that do it much faster, such as GrayscaleMBS
I can turn a color image to gray (24 bits) but I can’t find a way to set the image to 8 bits in RB.
How can you create a non 32 bits Picture Class ?
i think intern the picture class use always 32 bit for RGBA
for access pixel data from picture see .RGBSurface
Xojo hasn’t supported 8 bit images for many many years.
Annoyingly… For example, I often need monochrome bitmaps and frankly feel like I’m wasting 23 out of every 24 bits!
I never got into the subject more than that but what I thought I knew was that a color needs 6 hexadecimal numbers (ex. &cFFFFFF) so 24 bits should be enough right?
My version of RB is 2010 and there was no Alpha channel.
When I create an image I use NewPicture (Width, Height, 32 ) but with 24 I don’t see any difference.
If I use 8, the image is transformed into black and white.
So I was thinking of creating an 8-bit image and replacing the color of each pixel with the color of the original pixels calculated in grayscale.
I don’t know if this is clear or correct but here is where I am.
i not get what you will achieve.
do you will write an image converter (load/save)?
will you load an image into gray for display in window?
for gray use
or do you try to save memory?
outside of xojo there are image formats which use a color palette
so each pixel reference an index to this palette.
The extra 8 would be the alpha channel… the RGB are still 0…255 values
I was thinking of creating an 8-bit image
Just give up and create a 32 bit one.
Set the RGB values to equal amounts for greyscale.
I use Gray = 0.299R + 0.587G + 0.114*B (CIE formula).
I was wondering just because I found it in another language and it would make sense to have gray colors in one channel as all three (RGB) have the same value.
Yes it would, but you cannot do it in (any recent version of…) Xojo.
Instead, decide on your grey value and apply it to all 3 of red, green, and blue.
From documentation around 2004:
More Picture Properties
The following property determines the color depth (in bits):
Picture.Depth as Integer
Legal values are 0,1,2,4,8,16, and 32. A value of 0 indicates that this Picture is a vector rather than a raster image.
So maybe 2010 still supported a depth of 8.
Nothing new does, (and I have long been annoyed at the loss of this feature)
I will try with an array of bytes and see if it’s faster.
Yes, Jeff I can convert a picture in 8 bits with RB 2010 but you get a picture in black and white.
But I’m sure, Beatrix without Google can enlighten us.