• A5_DESIGN_BITMAP Function
• A5_GET_BITMAP Function
• A5_GET_BMP_FROM_FILE Function
• A5_GET_JPEG Function
• A5_IMAGE_TRANSFORM Function
• a5_ink_to_png Function
• BITMAP Function
• BITMAP_ALPHA Function
• BITMAP_COLORS_GET Function
• BITMAP_HEIGHT Function
• BITMAP_SATURATION Function
• BITMAP_SIZE Function
• Bitmap_to_JPEG Function
• BITMAP_TO_PALETTE_PNG Function
• BITMAP_TO_PNG Function
• BITMAP_TRANSLUCENT Function
• BITMAP_WIDTH Function
• CHANGE_COLOR Function
• CLIP_SHAPE Function
• Displaying and Printing Bitmaps
• DRAW_BOX Function
• DRAW_WRAP_SCRIPT Function
• DRAW_WRAP_TEXT Function
• EXTENT_HEIGHT Function
• EXTENT_WIDTH Function
• FILL_OVAL Function
• FILL_PIE Function
• FILL_POLY Function
• FILL_RECT Function
• FILL_ROUND_RECT Function
• FILL_SHAPE Function
• INNER_OVAL Function
• INNER_PIE Function
• INNER_POLY Function
• INNER_RECT Function
• INNER_ROUND_RECT Function
• INNER_SHAPE Function
• JPEG_TO_BITMAP Function
• LINE Function
• LINETO Function
• OVAL Function
• PIE Function
• PNG_TO_BITMAP Function
• POLY Function
• POLY_BEZIER Function
• RECT Function
• ROUND_RECT Function
• SET_FONT Function
• SET_ORIGIN Function
• SET_ROTATE Function
• SET_SCALE Function
• SET_UNITS Function
• SHAPE Function
• START_POLY Function
• TEXT Function
• TEXT_HEIGHT Function
• TEXT_WIDTH Function
• UI_BITMAP_CREATE Function
• UI_BITMAP_CREATE_FROM_SCREEN Function
• UI_BITMAP_CREATE_FROM_XPM Function
• UI_BITMAP_DRAW Function
• UI_BITMAP_DROP Function
• UI_BITMAP_INFO_GET Function
• UI_BITMAP_LOAD Function
• UI_BITMAP_PNG_LOAD Function
• UI_BITMAP_PNG_SAVE Function
• UI_BITMAP_SAVE Function
• UI_PRINTER_DRAW Function
• UI_SCREEN_DRAW Function
• UI_SHAPE_DESTROY Function
• UI_SHAPE_LINETO Function
• UI_SHAPE_OVAL Function
• UI_SHAPE_POLY Function
• UI_SHAPE_RECT Function
• UI_SHAPE_ROUND_RECT Function
• UI_SHAPE_START_POLY Function
• WINDOW_TO_IMAGE Function
• WRAP_TEXT_HEIGHT Function

BITMAP_ALPHA Function

Syntax

Arguments

bitmap_nameCharacter

The name of the bitmap to modify.

XPosNumeric

The horizontal coordinate of the upper left corner of the bitmap.

YPosNumeric

The vertical coordinate of the upper left corner of the bitmap.

level_bitmapCharacter

The name of the bitmap to use as the alpha channel. A pixel value of 0 is completely transparent. A pixel value of 255 is completely opaque. Intermediate values represent degrees of transparency.

Description

Draws a bitmap using a different bitmap an alpha-value.

Discussion

BITMAP_ALPHA() sets the transparency of each of the pixels in a bitmap according to the values of the corresponding pixels in an alpha channel bitmap, then draws the result.

Example

Get the original color image, then extract the color data and the alpha channel data.

png_data = file.to_blob("c:\documents\Xbasic Reference\Images\toucan.png")
rgb_data = png_to_bitmap(png_data, "R")
trans_data = png_to_bitmap(png_data, "A")

Create two bitmaps from the color data and the alpha channel data.

ui_bitmap_load("rgb", rgb_data)
ui_bitmap_load("trans", trans_data)

Calculate the positions of the three images.

pixsize = ui_bitmap_info_get(rgb_data, "w,h")
xpix = val( word(pixsize, 1, ",") )
ypix = val( word(pixsize, 2, ",") )
xperin = ui_info(4)
yperin = ui_info(5)
width = xpix/xperin
height = ypix/yperin

Combine the three images.

ui_bitmap_create("combine", width, height)
stone_data = file.to_blob("C:\WINDOWS\Greenstone.bmp")
ui_bitmap_load("Stone", stone_data)
ui_bitmap_draw("combine", <<%code%
bitmap("stone", 0, 0)
bitmap_alpha("rgb", 0, 0, "trans")
%code%)

Display the three images.

ui_dlg_box("image", <<%dlg% {image=rgb} {image=trans} {image=combine}
%dlg%)

Limitations

Used only in the Code sections of UI_BITMAP_DRAW(), UI_SCREEN_DRAW(), and UI_PRINTER_DRAW().

See Also

• Bitmap and Graphic Functions