LOADIMAGE: Difference between revisions

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{{Cl|END FUNCTION}}
{{Cl|END FUNCTION}}
{{CodeEnd}}
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{{Small|Code by Ted Weissgerber}}
{{Small|Adapted from example code by Terry Ritchie}}




Revision as of 22:39, 19 February 2023

The _LOADIMAGE function loads an image into memory and returns valid LONG image handle values that are less than -1.


Syntax

handle& = _LOADIMAGE(fileName$[, [mode&][, requirements$]])


Parameters

  • filename$ is literal or variable STRING file name value.
  • Optional mode& LONG values can be:
    • 32 = 32-bit image.
    • 33 = 32-bit hardware image.
    • 256 = 8-bit (256 color) image using the QB64-PE master palette.
    • 257 = 8-bit (256 color) image using an adaptive palette.
  • Optional requirements$ STRING values can be a combination of (version 3.6.0 and up):
    • HARDWARE: Loads the image as a 32-bit hardware image. This can be used instead of mode 33 (above).
    • ADAPTIVE: Loads the image an 8-bit (256 color) image using an adaptive palette. This can be used instead of mode 257 (above).
    • MEMORY: This will treat filename$ as a memory buffer containing the image file instead of a file name.


Description

  • Various common image file formats like JPG, PNG, TGA, BMP, PSD, GIF, HDR, PIC, PNM and PCX are supported. A path can also be given.
  • The mode& parameter can be 32, 33,256 or 257. Omit to use the current graphic screen settings.
  • Mode 33 images are hardware accelerated and are created using _LOADIMAGE or _COPYIMAGE (version 1.000 and up).
  • Mode 256 images are loaded using the QB64-PE master palette. This is the same palette that is used for 256 color screens like SCREEN 13.
  • Mode 257 images are loaded using an adaptive palette making these images look better than mode 256 when used with 32-bit color screens (version 3.1.0 and up).
  • Loaded images can be read invisibly using POINT. Image coordinates start at 0 up to the _WIDTH - 1 and _HEIGHT - 1.
  • Images can be made into a program SCREEN or page adopting the size and palette settings or placed using _PUTIMAGE.
  • Returns -1 as an invalid handle if it can't load the image. Valid LONG handle returns are less than -1 (handle& < -1).
  • Valid images only need to be loaded once. The handle can be used repeatedly until freed.
  • Images are not deallocated when the SUB or FUNCTION they are created in ends. Free them with _FREEIMAGE.

Errors

  • Some picture file images may not load when a mode& value is designated. Try loading it without a mode& designation.
  • It is important to free unused or discarded images with _FREEIMAGE to prevent CPU memory overflow errors.
  • In text-only SCREEN 0, mode& 32 must be specified. When loading an _ICON image use 32 for the mode& too.


Availability

  • v0.800

    v0.800

  • all

    all

  • Apix.png
  • yes

    yes

  • yes

    yes

  • yes

    yes

  • Mode 33 was added in QB64 v1.0, which makes it also available in all QB64-PE versions.
  • Mode 257 was added in QB64-PE v3.1.0, hence it's not available in the original QB64 versions.
  • In QB64-PE v3.6.0 this function got a new optional parameter requirements$ and the ability to load image files from memory.


Examples

Example 1
To display an image in 32-bit color using its resolution as a program screen.
i& = _LOADIMAGE("mypic.jpg", 32)
SCREEN i&
Example 2
DRAWing and rotating an image 360 degrees using Turn Angle. POINT is used to read the invisible image source.
SCREEN _NEWIMAGE(800, 600, 32)
img& = _LOADIMAGE("QB64.PNG")                           'use any 24/32 bit image

wide% = _WIDTH(img&): deep% = _HEIGHT(img&)
TLC$ = "BL" + STR$(wide% \ 2) + "BU" + STR$(deep% \ 2)  'start draw at top left corner
RET$ = "BD BL" + STR$(wide%)                            'return to left side of image
_SOURCE img&
_DEST 0
DO
  FOR angle% = 0 TO 360 STEP 15
    CLS
    DRAW "BM400, 300" + "TA=" + VARPTR$(angle%) + TLC$
    FOR y = 0 TO deep% - 1
      FOR x = 0 TO wide% - 1
        DRAW "C" + STR$(POINT(x, y)) + "R1"            'color and DRAW each pixel
      NEXT
      DRAW RET$
    NEXT
    _DISPLAY                         'NOTE: CPU usage will be HIGH!
  NEXT
LOOP UNTIL INKEY$ > ""
Code by Ted Weissgerber


Example 3
To load an image from memory and display it on the screen
OPTION _EXPLICIT

DIM Bee& '                                               the image file
DIM cx%, cy% '                                           center x,y coordinate for image

RESTORE Data_tbee0_png_2314
Bee& = _LOADIMAGE(LoadResource, 32, "memory") '          load image file into memory
SCREEN _NEWIMAGE(640, 480, 32) '                         enter a graphics screen
CLS , _RGB32(127, 127, 127) '                            clear the screen with gray
LOCATE 2, 15 '                                           position text cursor
PRINT "An image loaded into memory and placed on the screen."
cx% = (640 - _WIDTH(Bee&)) \ 2 '                         calculate x center position
cy% = (480 - _HEIGHT(Bee&)) \ 2 '                        calculate y center position
_PUTIMAGE (cx%, cy%), Bee& '                             place image onto center of screen
SLEEP '                                                  wait for key stroke
_FREEIMAGE Bee& '                                        remove image from memory
SYSTEM '                                                 return to OS


Data_tbee0_png_2314:
DATA 2314,2988,-1
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' Convert a base64 string to a normal string
FUNCTION DecodeBase64$ (s AS STRING)
    CONST BASE64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"

    DIM AS STRING buffer, result
    DIM AS _UNSIGNED LONG i
    DIM AS _UNSIGNED _BYTE char1, char2, char3, char4

    FOR i = 1 TO LEN(s) STEP 4
        char1 = INSTR(BASE64_CHARACTERS, CHR$(ASC(s, i))) - 1
        char2 = INSTR(BASE64_CHARACTERS, CHR$(ASC(s, i + 1))) - 1
        char3 = INSTR(BASE64_CHARACTERS, CHR$(ASC(s, i + 2))) - 1
        char4 = INSTR(BASE64_CHARACTERS, CHR$(ASC(s, i + 3))) - 1
        buffer = CHR$(_SHL(char1, 2) OR _SHR(char2, 4)) + CHR$(_SHL(char2 AND 15, 4) OR _SHR(char3, 2)) + CHR$(_SHL(char3 AND 3, 6) OR char4)

        result = result + buffer
    NEXT

    ' Remove padding
    IF RIGHT$(s, 2) = "==" THEN
        result = LEFT$(result, LEN(result) - 2)
    ELSEIF RIGHT$(s, 1) = "=" THEN
        result = LEFT$(result, LEN(result) - 1)
    END IF

    DecodeBase64 = result
END FUNCTION


' Loads a binary file encoded with Bin2Data
' Usage:
'   1. Encode the binary file with Bin2Data
'   2. Include the file or it's contents
'   3. Load the file like so:
'       Restore label_generated_by_bin2data
'       Dim buffer As String
'       buffer = LoadResource   ' buffer will now hold the contents of the file
FUNCTION LoadResource$
    DIM AS _UNSIGNED LONG ogSize, resize
    DIM AS _BYTE isCompressed

    READ ogSize, resize, isCompressed ' read the header

    DIM AS STRING buffer, result

    ' Read the whole resource data
    DO WHILE LEN(result) < resize
        READ buffer
        result = result + buffer
    LOOP

    ' Decode the data
    buffer = DecodeBase64(result)

    ' Expand the data if needed
    IF isCompressed THEN
        result = _INFLATE$(buffer, ogSize)
    ELSE
        result = buffer
    END IF

    LoadResource = result
END FUNCTION
Adapted from example code by Terry Ritchie


More examples


See also


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