SaveImage SUB
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- Bitmaps can be 1, 4, 8 or 24/32 bits per pixel(BPP) color palettes. QB64 is capable of working with high color bitmaps.
- Screen or Image width and height calculations are automatically made using the image handle value.
- Use an image handle value of zero(0) to get a screen shot of the entire active program screen.
- Note: SCREEN 0 text mode cannot be screen saved in QBasic or QB64 using this SUB.
Examples
- Example
- Using the SaveImage SUB program to save a loaded 32 bit PNG image as a bitmap (BMP) using QB64's graphic functions.
'load a 32 bit .PNG file image i& = _LOADIMAGE("source\peLogo.png", 32) IF i& < -1 THEN 'load success: get image's width/height w& = _WIDTH(i&): h& = _HEIGHT(i&) 'TEST-1: directly save the loaded image as .BMP file "logo.bmp" SaveImage i&, "logo" 'TEST-2: make a new 4:3 program SCREEN of the loaded image's width/height SCREEN _NEWIMAGE((4 * w&), (3 * h&), 32) 'now tile-fill the screen with the loaded image FOR x& = 0 TO (4 * w&) STEP w& FOR y& = 0 TO (3 * h&) STEP h& _PUTIMAGE (x&, y&), i& NEXT y& NEXT x& 'and then save the entire program screen as "screenshot.bmp" SaveImage 0, "screenshot" ELSE 'load failure: print error PRINT "Cannot find/load the given image." END IF END SUB SaveImage (image AS LONG, filename AS STRING) bytesperpixel& = _PIXELSIZE(image&) IF bytesperpixel& = 0 THEN PRINT "Text modes unsupported!": END IF bytesperpixel& = 1 THEN bpp& = 8 ELSE bpp& = 24 x& = _WIDTH(image&) y& = _HEIGHT(image&) b$ = "BM????QB64????" + MKL$(40) + MKL$(x&) + MKL$(y&) + MKI$(1) + MKI$(bpp&) + MKL$(0) + "????" + STRING$(16, 0) 'partial BMP header info(???? to be filled later) IF bytesperpixel& = 1 THEN FOR c& = 0 TO 255 ' read BGR color settings from JPG image + 1 byte spacer(CHR$(0)) cv& = _PALETTECOLOR(c&, image&) ' color attribute to read. b$ = b$ + CHR$(_BLUE32(cv&)) + CHR$(_GREEN32(cv&)) + CHR$(_RED32(cv&)) + CHR$(0) 'spacer byte NEXT END IF MID$(b$, 11, 4) = MKL$(LEN(b$)) ' image pixel data offset(BMP header) lastsource& = _SOURCE _SOURCE image& IF ((x& * 3) MOD 4) THEN padder$ = STRING$(4 - ((x& * 3) MOD 4), 0) FOR py& = y& - 1 TO 0 STEP -1 ' read JPG image pixel color data r$ = "" FOR px& = 0 TO x& - 1 c& = POINT(px&, py&) 'POINT 32 bit values are large LONG values IF bytesperpixel& = 1 THEN r$ = r$ + CHR$(c&) ELSE r$ = r$ + LEFT$(MKL$(c&), 3) NEXT px& d$ = d$ + r$ + padder$ NEXT py& _SOURCE lastsource& MID$(b$, 35, 4) = MKL$(LEN(d$)) ' image size(BMP header) b$ = b$ + d$ ' total file data bytes to create file MID$(b$, 3, 4) = MKL$(LEN(b$)) ' size of data file(BMP header) IF LCASE$(RIGHT$(filename$, 4)) <> ".bmp" THEN ext$ = ".bmp" f& = FREEFILE OPEN filename$ + ext$ FOR OUTPUT AS #f&: CLOSE #f& ' erases an existing file OPEN filename$ + ext$ FOR BINARY AS #f& PUT #f&, , b$ CLOSE #f& END SUB |
SUB Explanation: b$ and d$ assemble the entire string of data to create a bitmap file. Some of the bitmap header info is placed later using a MID$ to add final header numerical data converted to ASCII characters by MKI$ or MKL$.
After the header, the RGB color settings are created using ASCII characters read backwards as Blue, Green, Red and CHR$(0) as a spacer. MKL$ places the byte values in reverse order too. Bitmaps and icons require that format. LEFT$ trims off the _ALPHA byte.
The actual image is read as pixel attributes from the image bottom to the top for proper formatting with zero padding when necessary.
Note: 32-bit images will be saved as 24-bit BMP files. All palette indexed images/modes will be saved as 256 color BMP files. Text modes cannot be saved.
See also
- _LOADIMAGE, _ICON, $EXEICON
- SCREEN
- TYPE, MKI$, MKL$
- Program ScreenShots (member SUB program)
- ThirtyTwoBit SUB (member SUB captures selected area)
- ThirtyTwoBit MEM SUB (Fast SUB uses memory instead of POINT)
- SaveIcon32 (converts any image to icon)
- Bitmaps, Icons and Cursors