Creating a Low Resolution Viewfile


When you create an image database, you may want to have a low resolution viewfile to represent a higher resolution image. Typically, the viewfile would be used when you want to quickly put an image on the screen, without moving megabytes of data.

The following script illustrates a technique for creating a low resolution viewfile on the fly. Presumably, you would save the viewfiles you create along side their higher resolution partners. This script was attached to the OnFetch() event of a form with an image control named bitmap1. and a text field named Fname.

dim imag as B
dim pth as C
dim fptr as P
pth = a5.get_path()+ chr(92)

Test whether we have a filename for the picture in the control Fname. If yes, then read the picture into a blob variable named imag. Next, load imag into a memory buffer named hres with UI_BITMAP_LOAD().

if (alltrim(Fname.text) <> "") then
    imag = file.to_blob(Fname.text)
    ui_bitmap_load("hres", imag)

Create a new memory buffer named lres with UI_BITMAP_CREATE(), then fill it with a stretched version of hres.

ui_bitmap_create("lres", 4, 3)
    ui_bitmap_draw("lres", <<%code%
    bitmap("hres", 0, 0, 4, 3, "stretch")

Move the memory buffer named lres into the imag variable with UI_BITMAP_SAVE() and save it to disk with <FILE>.WRITEB() . Remove the lres and hres buffers from memory.

imag = ui_bitmap_save("lres")
    fptr = file.create(pth + "lres.bmp", FILE_RW_EXCLUSIVE)

Display the low resolution image on the form. If there was no high resolution image to display, display white.bmp.

bitmap1.bitmap.filename = pth + "lres.bmp"
    bitmap1.bitmap.filename = pth + "white.bmp"
end if