[Newbies] [Q] Creating Form from ByteArray

[Bert Freudenberg]

On 11.06.2014, at 00:36, Sungjin Chun <chunsj at castlesoft.co.kr> wrote:

> Hi,
> 
> I want to draw gray scale bitmap using byte array which has pixel by pixel gray
> scale value as byte like this;
> 
> [0 0 0 0 0 0 0 0
>  16 23 255 78 12 12 12 12
> ...
> ...] (8x4 for example)
> 
> I can draw this using Pen class pixel by pixel manner but this is very slow and 
> I think there should be faster way of creating a Form using above byte array.

If the width is a multiple of 4, you can use the byte array directly as form bits:

| w h bytes form |
w := 100.
h := 60.
bytes := ((1 to: w*h) collect: [:i | 256 atRandom - 1]) asByteArray.
form := ColorForm extent: w at h depth: 8 bits: bytes.
form colors: ((0 to: 255) collect: [:i | Color gray: i / 255]).
form display

This would be the best and fastest way. If the width is not a multiple of 4 then perhaps you can add the necessary padding when creating the byte array. Otherwise, a very fast way is to use BitBlt to copy whole lines from the byte array to the form. 

But even creating a byte array with the right padding just using at:put: would be a lot faster than using a Pen.

- Bert -


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