Thumbnail creation during Image Upload

Question

In my application, I am able to upload documents to content server using KPRO API's.  Image upload works fine and I can display the same file in webdynpro image UI element. Now while uploading the image, i also need to create a thumbnail image and store it. I can use these thumbnail images for image navigation instead of actual file due to performance issues.
How to create thumbnail images from jpeg image file?
Edited by: ashwinsrinivas on Jul 20, 2010 8:41 PM

Answer 1

I'm trying to put the results of my tinkering into a blog - which should hopefully get published in the next few days.
But just to update you here first
Yes it can be done! - here's the proof:
[Large image about to be resize to a thumbnail|https://weblogs.sdn.sap.com/weblogs/images/251723740/large_double_rainbow.jpg]
[Image after resizing|https://weblogs.sdn.sap.com/weblogs/images/251723740/resized_rainbow.jpg]
Thought I'd go with some double rainbows to be topical (plus I can't get the darn song out of my head!)
I created a new method in Thomas' class: TRANSFORM_RESIZE with 2 input parameters of type i, new_width and new_height.
Then most of the code is pretty similar to the rotation code that Thomas had already written...
data l_data type xstring.
  data l_new_data type xstring.
  data l_row type xstring.
  data l_new_row type xstring.
  data l_num_pixels type i.
  data l_counter type i.
  data l_counter2 type i.
  data l_len type i.
  data l_pad type i.
  data l_mod type i.
  data l_width type i.
  data l_bytes_per_pixel type i.
  data: l_y_factor type f,
        l_x_factor type f.
  data l_new_pad type i.
  data l_null(1) type x.
* get the data from the image representation
  l_data = gx_content+data_offset.
  l_bytes_per_pixel = bpp / 8.
  l_width = width * l_bytes_per_pixel.
  l_y_factor = height / new_height.
  l_x_factor = width / new_width.
  l_mod = l_width mod 4.
  l_pad = 4 - l_mod.
  if l_pad = 4.
    l_pad = 0.
  endif.
  l_len = xstrlen( l_data ).
  data lt_rows type standard table of xstring.
  data: l_row_index type i.
  field-symbols <wa_row> like line of lt_rows.
  do new_height times.
    l_row_index = floor( ( sy-index - 1 ) * l_y_factor ).
    l_counter = l_row_index * ( l_width + l_pad ).
    append initial line to lt_rows assigning <wa_row>.
    <wa_row> = l_data+l_counter(l_width).
  enddo.
  l_mod = ( new_width * l_bytes_per_pixel ) mod 4.
  l_new_pad = 4 - l_mod.
  if l_new_pad = 4.
    l_new_pad = 0.
  endif.
  loop at lt_rows assigning <wa_row>.
    clear l_new_row.
    do new_width times.
      l_counter2 =  l_bytes_per_pixel * floor( ( sy-index - 1 ) * l_x_factor ).
      concatenate l_new_row <wa_row>+l_counter2(l_bytes_per_pixel)  into l_new_row in byte mode.
    enddo.
    if l_new_pad > 0.
      do l_new_pad times.
        concatenate  l_new_row l_null into l_new_row in byte mode.
      enddo.
    endif.
    concatenate  l_new_data l_new_row into l_new_data in byte mode.
  endloop.
  data x_new_image type xstring.
  concatenate gx_content(data_offset) l_new_data into x_new_image in byte mode.
  data x_header type xstring.
  x_header = gx_content+0(data_offset).
  data x_size(4) type x.
  data i_size type i.
  i_size = xstrlen( x_new_image ).
  write4 i_size x_size.
  concatenate x_header+0(2) x_size x_header+6 into x_header in byte mode.
  data x_data_size(4) type x.
  data i_data_size type i.
  i_data_size = xstrlen( l_new_data ).
  write4 i_data_size x_data_size.
  concatenate x_header+0(34) x_data_size x_header+38 into x_header in byte mode.
  data x_width(4) type x.
  data x_height(4) type x.
  data i_width type i.
  data i_height type i.
  i_width = new_width.
  i_height = new_height.
  write4 i_width x_width.
  write4 i_height x_height.
  concatenate x_header+0(18) x_width x_height x_header+26 into x_header in byte mode.
  data x_hres(4) type x.
  data x_vres(4) type x.
  x_hres = x_header+38(4).
  x_vres = x_header+42(4).
  concatenate x_header+0(38) x_vres x_hres x_header+46 into x_header in byte mode.
  concatenate x_header  l_new_data into x_new_image in byte mode.
  gx_content = x_new_image.
  me->read_bitmap_header( ).