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VB6 MemoryDC

A memory DC class written in VB6. You can use this class to create and operate memory DCs easily.

Usage

Initalizing MemoryDC class

To declare a MemoryDC typed variable, simply

Dim memDC As New clsMemDC

Next, you should create the DC when you need it:

memDC.CreateMemDC image_width, image_height

For function CreateMemDC, please refer its description in "Functions Description" section.

Deleting MemoryDC class

When you no longer need the MemoryDC typed variable, simply

memDC.DeleteMemDC
Set memDC = Nothing

Painting from other DCs

To paint the image from other DCs, simply

memDC.BitBltFrom YourDC, FromX, FromY, ToX, ToY, image_width, image_height

For function BitBltFrom, please refer its description in "Functions Description" section.

Painting to other DCs

To paint the image to other DCs, simply

memDC.BitBltTo YourDC, ToX, ToY, FromX, FromY, image_width, image_height

For function BitBltTo, please refer its description in "Functions Description" section.

Copying bit data to a Byte array

To copy the bit data of the image in the DC to a Byte array, simply

memDC.CopyDataTo data     'data is a Byte() typed array variable

For function CopyDataTo, please refer its description in "Functions Description" section.

Copying bit data from a Byte array

To copy the bit data of the image in the DC from a Byte array, simply

memDC.CopyDataFrom data     'data is a Byte() typed array variable

For function CopyDataFrom, please refer its description in "Functions Description" section.

For more functionalities, please read the following sections.

Functions Description

CreateMemDC function

CreateMemDC function sets the memory DC information (width, height, bit count) and creates it.

Definition

Public Function CreateMemDC(ByVal iWidth As Long, ByVal iHeight As Long, _
    Optional ByVal iBitCount As Integer = 16, Optional ByVal FromHdc As Long = 0) As Boolean

Parameters

iWidth: Long, the width of the memory DC being created.

iHeight: Long, the height of the memory DC being created.

iBitCount: Optional, Integer, the color bit count of the memory DC being created. Default is 16 bit.

FromHdc: Optional, Long, the source DC handle. Default is 0.

Return value

Type: Boolean

If the memory DC is created successfully, the function returns True. Otherwise, the function returns False.

Examples

memDC.CreateMemDC 1920, 1080      'Creates a 1920 * 1080 memory DC
memDC.CreateMemDC 1920, 1080, 8   'Creates a 1920 * 1080, 8 bit memory DC
memDC.CreateMemDC 1920, 1080, , frmMain.hDC   'Creates a 1920 * 1080 memory DC from frmMain's hDC

NOTE: When you use CreateMemDC function, this function deletes the previous memory DC automatically.

DeleteMemDC function

DeleteMemDC deletes the create memory DC.

Definition

Public Sub DeleteMemDC()

Examples

memDC.DeleteMemDC

NOTE: Call DeleteMemDC when you don't need the memory DC anymore. This function is automatically called when the class is being terminated.

BitBltFrom function

BitBltFrom paints image from other DCs to the created memory DC.

Definition

Public Function BitBltFrom(FromHdc As Long, FromX As Long, FromY As Long, _
    ToX As Long, ToY As Long, iWidth As Long, iHeight As Long, _
    Optional DrawMode As RasterOpConstants = vbSrcCopy Or BITBLT_TRANSPARENT_WINDOWS) As Boolean

Parameters

FromHdc: Long, Specifics the DC handle to paint image from.

FromX: Long, X position of the original image.

FromY: Long, Y position of the original image.

ToX: Long, X position of the target image.

ToY: Long, Y position of the target image.

iWidth: Long, width of the image being painted

iHeight: Long, height of the image being painted

DrawMode: Optional, RasterOpConstants, specifics painting mode. Default is vbSrcCopy Or BITBLT_TRANSPARENT_WINDOWS. Painting mode can be the combination of the following constants:

RasterOpConstants
vbDstInvert
vbMergeCopy
vbMergePaint
vbNotSrcCopy
vbNotSrcErase
vbPatCopy
vbPatInvert
vbPatPaint
vbSrcAnd
vbSrcCopy
vbSrcErase
vbSrcInvert
vbSrcPaint

Return value

Type: Boolean

If the image is painted successfully, the function returns True. Otherwise, the function returns False.

Examples

memDC.BitBltFrom frmMain.hDC, 0, 0, 0, 0, 100, 100      'Paints the image from frmMain.hDC, from (0, 0) of the window to (0, 0) of the memory DC, sized 100 * 100
memDC.BitBltFrom GetDC(0), 100, 200, 150, 250, 300, 400, vbSrcInvert      'Paints the image from the screen DC, from (100, 200) of the screen to (150, 250) of the memory DC, sized 300 * 400, using vbSrcInvert painting mode

BitBltTo function

BitBltTo paints image from the created memory DC to other DCs.

Definition

Public Function BitBltTo(ToHdc As Long, ToX As Long, ToY As Long, _
    FromX As Long, FromY As Long, iWidth As Long, iHeight As Long, _
    Optional DrawMode As RasterOpConstants = vbSrcCopy Or BITBLT_TRANSPARENT_WINDOWS) As Boolean

Parameters

ToHdc: Long, Specifics the DC handle to paint image to.

ToX: Long, X position of the target image.

ToY: Long, Y position of the target image.

FromX: Long, X position of the original image.

FromY: Long, Y position of the original image.

iWidth: Long, width of the image being painted

iHeight: Long, height of the image being painted

DrawMode: Optional, RasterOpConstants, specifics painting mode. Default is vbSrcCopy Or BITBLT_TRANSPARENT_WINDOWS. For constants available for DrawMode, please refer to "BitBltFrom function" section.

Return value

Type: Boolean

If the image is painted successfully, the function returns True. Otherwise, the function returns False.

Examples

memDC.BitBltTo frmMain.hDC, 0, 0, 0, 0, 100, 100      'Paints the image to frmMain.hDC, from (0, 0) of the memory DC to (0, 0) of the window, sized 100 * 100
memDC.BitBltTo GetDC(0), 100, 200, 150, 250, 300, 400, vbSrcInvert      'Paints the image to the screen DC, from (100, 200) of the memory DC to (150, 250) of the screen DC, sized 300 * 400, using vbSrcInvert painting mode

CopyDataFrom function

CopyDataFrom function copies data from a Byte array to the memory DC.

Definition

Public Sub CopyDataFrom(FromArray() As Byte)

Parameters

FromArray: Byte(), the Byte array to copy data from.

Examples

memDC.CopyDataFrom data         'Copy image data from data, where data is a Byte array

NOTE: CopyDataFrom function copies all data from the array to the memory region of the memory DC. So it checks if the array size is larger than the size of memory region of the memory DC or not. If the memory region is smaller than the size of the array, it only copies data in the same size to the size of memory region of the memory DC. For example, if the array is 10 bytes, and the size of the memory region of the memory DC is 5 bytes, this function will only copy 5 bytes from the array.

CopyDataTo function

CopyDataTo function copies data from the memory DC to a Byte array.

Definition

Public Function CopyDataTo(ToArray() As Byte) As Boolean

Parameters

ToArray: Byte(), the Byte array to copy data to.

Return value

Type: Boolean

If the data is copied successfully, the function returns True. Otherwise, the function returns False.

Examples

memDC.CopyDataTo data         'Copy image data to data, where data is a Byte array

NOTE: CopyDataTo function copies all data from the memory region of the memory DC to the array. So it checks if the array size is large enough to receive the memory DC data or not. If the memory region is larger than the size of the array, this function fails. For example, if the array is 5 bytes, and the size of the memory region of the memory DC is 10 bytes, this function will return False

Properties Description

iWidth: Long, the width of the memory DC.

iHeight: Long, the height of the memory DC.

iBitCount: Long, the color bit count of the memory DC.

iImageSize: Long, the size of the memory region of the memory DC.

hDC: Long, the handle to the created memory DC.

hBmp: Long, the handle to the bitmap created. This bitmap is created together with the memory DC.

lpBitData: Long, the address of the memory region of the memory DC.

License

MIT