How to create an image from scratch?

General
1

Hi everybody,
I’m actually testing XoJo which is very good product. I 've a basic question.
How to create by my self a simple RGBA image?
I’ve tested unsuccessfully this code
What’s is wrong
Thanks a lot and regards from France

 Dim pic As  new Picture (160,120)
 DIM  mbRGBA as new MemoryBlock (160 * 120 * 4)  

  dim offset as integer
  offset =0
  
  for i = 0 to 119
    for j = 0 to 159
      mbRGBA.Byte(offset) = 255
      mbRGBA.Byte(offset + 1) = 0
      mbRGBA.Byte(offset + 2) = 0
      mbRGBA.Byte(offset + 3) = 0
      offset = offset + 4
    next j
  next i

  pic = Picture.FromData(mbRGBA)
  
  Imagewell1.Image = pic
2

What exactly are you trying to do?
It looks like you are trying to build an image byte by byte…
Is there a reason you can not DRAW your picture and then save it using the desired format, and let the system figure out the internal encoding required?

Plus I think your “format” is wrong… there is no header information (required even by a simple BMP format)

3

maybe better use new picture, than get RGBSurface and change pixels?

4

Thanks for replies
In fact I’m using OpenCV associated to XoJo for processing binaries thermical images (very easy with Declare)
This code is OK

  For i = 0 To n step 2
    lo = sbin.ReadByte()                                               'low byte for grayscale
    mbPixels.byte(index) = lo                                     
    hi =sbin.ReadByte()                                                  'high byte for Temperature calculus
    temperature =((hi * 256+ lo) -1000)  / 10             'temp in degrees
    mbTemperatures.Byte(index) = hi
    TemperatureTotale.Append (temperature)             'store temperature in array
    for j = 0 to 3
      mbRGBA.Byte (j + (index * 4)) = lo                       'create A RGBA image : OK A channel not processed by OpenCV
    next
    index= index + 1
  Next

and this instruction cvSetData(src, mbRGBA, 160 * 4 ) creates a perfect 4-channel image than OpenCV can use
src is just a pointer to an image structure
I’m just wondering why Picture.FromData(mbRGBA) does not work
Regards

5

Thanks Christian
Your suggestion was right: using RBGSurface is perfect in association with a MemoryBlock used to store binary values :slight_smile:
Can be used whatever the number of channels of the binary image

  dim lastX as integer = pic.Width -1
  dim lastY as integer = pic.Height - 1
  
  
  index = 0
  nChannels = 1
  For y As Integer = 0 To endY
    For x As Integer = 0 To endX
      index= (y * 160) + (x * nChannels) 
      aColor= RGB(mbPixels.Byte(index), mbPixels.Byte(index), mbPixels.Byte(index), 0)
      pic.RGBSurface.Pixel(x,y) = aColor
    next
  next
  
  // Display the picture
  Pic.Graphics.DrawPicture(pic, 0,0)
  Imagewell1.Image = pic