BlitzMax/Modules/Graphics/Max2D

From Wikibooks, open books for an open world
Jump to: navigation, search

The Max2D module provides a set of commands for drawing 2D graphics.

Before using any of the Max2D commands, you must first create a Max2D graphics object. The easiest way to do this is using the Graphics command.

By default, Max2D is double buffered which means you will have to use Flip once you have finished drawing each frame of graphics.

Drawing[edit]

Max2D provides support for the following drawing commands:

Drawing command Action
Cls Clears the viewport
Plot Draws a single pixel
DrawLine Draws a line
DrawRect Draws a rectangle
DrawOval Draws an oval
DrawPoly Draws a polygon
DrawText Draws some text
DrawImage Draws an image
DrawPixmap Draws a pixmap

Viewport, origin and handle[edit]

Drawing commands are clipped to a rectangular area known as the viewport. Only the area within the viewport is ever modified, and attempting to draw outside the viewport will result in the drawing command being clipped or chopped to the viewport. To set the viewport, use the SetViewport command.

Drawing commands are also offset by the current origin and handle. To set these properties, use the SetOrigin and SetHandle commands.

The current handle is an x,y coordinate subtracted from all drawing x,y coordinates before any rotation or scaling occurs. This allows you to provide a local 'center' for drawing. On the other hand, the current origin is an x,y coordinate added to all drawing x,y coordinates after any rotation or scaling.

Color, alpha and blend mode[edit]

Drawing commands are affected by the current color, alpha and blend mode. You can set these properties by using the SetColor, SetAlpha and SetBlend commands.

The current alpha value controls the transparency level when using the ALPHABLEND blend mode.

The current blend mode controls how pixels are combined with existing pixels in the back buffer and can be one of the following:

Blend mode Effect
SOLIDBLEND Pixels overwrite existing backbuffer pixels
MASKBLEND Pixels are drawn only if their alpha component is greater than .5
ALPHABLEND Pixels are alpha blended with existing backbuffer pixels
LIGHTBLEND Pixel colors are added to backbuffer pixel colors, giving a 'lighting' effect
SHADEBLEND Pixel colors are multiplied with backbuffer pixel colors, giving a 'shading' effect

Rotation and scale[edit]

Drawing commands can be scaled and rotated using the SetScale and SetRotation commands. Rotation and scaling occur relative to the current handle.

Images[edit]

Images are pre-rendered chunks of graphics that can be efficiently drawn using a single DrawImage command. Images are typically stored in png, bmp or jpg format, and can be loaded using the LoadImage command.

Image drawing is also affected by color, alpha, blend, rotation and scale. The current color is multiplied with each pixel color before the image is drawn to the backbuffer, allowing you to tint images. To disable this effect, you should set the current color to white.

Images can also have a mask color. This is the color that represents transparency when an image is drawn using the MASKBLEND blend mode. To set the mask color, use the SetMaskColor command.

Images can be created by snapshotting regions of the back buffer using the GrabImage command.

Pixmaps[edit]

Pixmaps are used to manipulate images at a pixel level, see the pixmaps module for details.

LockImage allows for direct Image pixel access and requires a corresponding call to UnlockImage when you have finished reading or modifying the pixels. The DrawPixmap and GrabPixmap commands allow you to move pixels to and from the current graphic display's backbuffer.

Collisions[edit]

Max2D features a multilayered pixel perfect collision system. The CollideRect and CollideImage commands provide a dual function allowing the drawing and hit testing of Rects and Images with any combination of 32 collision layers. The current Scale, Rotation, Origin and Handle settings are taken into account so coordinates for the collision commands accurately match their drawing counterparts DrawRect and DrawImage. ResetCollisions is used to clear any or all of the 32 collision layers provided.

Functions[edit]

Cls[edit]

Function Cls()

Description: Clear graphics buffer

Information: Clears the graphics buffer to the current cls color as determined by SetClsColor.

Example:

' cls.bmx

' a spinning text message
' remove the call to cls to illustrate the
' need for clearing the screen every frame

Graphics 640,480
SetOrigin 320,240
While Not KeyHit(KEY_ESCAPE)
        Cls 
        SetRotation frame
        DrawText "Press Escape To Exit",0,0
        Flip
        frame:+1
Wend

SetClsColor[edit]

Function SetClsColor( red,green,blue )

Description: Set current Cls color

Information: The red, green and blue parameters should be in the range of 0 to 255.

The default cls color is black.

GetClsColor[edit]

Function GetClsColor( red Var,green Var,blue Var )

Description: Get red, green and blue component of current cls color.

Returns: Red, green and blue values in the range 0..255 in the variables supplied.

Plot[edit]

Function Plot( x#,y# )

Description: Plot a pixel

Information: Sets the color of a single pixel on the back buffer to the current drawing color defined with the SetColor command. Other commands that affect the operation of Plot include SetOrigin, SetViewPort, SetBlend and SetAlpha.

Example:

' plot.bmx

' plots a cosine graph
' scrolls along the graph using an incrementing frame variable 

Graphics 640,480

While Not KeyHit(KEY_ESCAPE)
        Cls
        For x=0 To 640
                theta=x+frame
                y=240-Cos(theta)*240
                Plot x,y
        Next
        frame=frame+1
        Flip
Wend

DrawRect[edit]

Function DrawRect( x#,y#,width#,height# )

Description: Draw a rectangle

Information: Sets the color of a rectangular area of pixels using the current drawing color defined with the SetColor command.

Other commands that affect the operation of DrawRect include SetHandle, SetScale, SetRotation, SetOrigin, SetViewPort, SetBlend and SetAlpha.

Example:

' drawrect.bmx

' draws a sequence of rectangles across the screen with
' increasing rotation and scale

' uses the frame variable to cycle through the values 0..9 for
' an animation effect between frames 

Graphics 640,480

SetBlend ALPHABLEND
SetAlpha 0.2

While Not KeyHit(KEY_ESCAPE)
        Cls
        DrawText "DrawRect Example",0,0
        For r=t To t+500 Step 10
                SetRotation r
                SetScale r/5,r/5
                DrawRect r,r,2,2
        Next
        t=t+1
        If t=10 t=0
        Flip    
Wend

DrawLine[edit]

Function DrawLine( x#,y#,x2#,y2#,draw_last_pixel=True )

Description: Draw a line

Information: DrawLine draws a line from x, y to x2, y2 with the current drawing color.

BlitzMax commands that affect the drawing of lines include SetLineWidth, SetColor, SetHandle, SetScale, SetRotation, SetOrigin, SetViewPort, SetBlend and SetAlpha. The optional draw_last_pixel parameter can be used to control whether the last pixel of the line is drawn or not. Not drawing the last pixel can be useful if you are using certain blending modes.

Example:

' drawline.bmx

' draws a cross hair at the mouse position using DrawLine

Graphics 640,480

HideMouse 

While Not KeyHit(KEY_ESCAPE)
        Cls
        x=MouseX()
        y=MouseY()
        DrawLine 320,240,x,y
        DrawLine x-2,y,x-10,y
        DrawLine x+2,y,x+10,y
        DrawLine x,y-2,x,y-10
        DrawLine x,y+2,x,y+10
        Flip
Wend

DrawOval[edit]

Function DrawOval( x#,y#,width#,height# )

Description: Draw an oval

Information: DrawOval draws an oval that fits in the rectangular area defined by x, y, width and height parameters.

BlitzMax commands that affect the drawing of ovals include SetColor, SetHandle, SetScale, SetRotation, SetOrigin, SetViewPort, SetBlend and SetAlpha.

Example:

' drawoval.bmx

' draws a pair of eyes using 4 DrawOval commands, 2 white, 2 blue
' positions the blue ovals so the eyes track the mouse

Graphics 640,480
While Not KeyHit(KEY_ESCAPE)
        Cls
        SetColor 255,255,255
        DrawOval 0,0,320,200
        DrawOval 320,0,320,200
        SetColor 0,0,255
        x=(MouseX()-320)/10
        y=(MouseY()-240)/10
        DrawOval 220-32+x,100+y,64,40
        DrawOval 420-32+x,100+y,64,40
        Flip
Wend

DrawPoly[edit]

Function DrawPoly( xy#[] )

Description: Draw a polygon

Information: DrawPoly draws a polygon with corners defined by an array of x#,y# coordinate pairs.

BlitzMax commands that affect the drawing of polygons include SetColor, SetHandle, SetScale, SetRotation, SetOrigin, SetViewPort, SetBlend and SetAlpha.

Example:

' drawpoly.bmx

' draws a simple triangle using the
' DrawPoly command and an array of
' floats listed as 3 pairs of x,y
' coordinates

Local tri#[]=[0.0,0.0,100.0,100.0,0.0,100.0]

Graphics 640,480
While Not KeyHit(KEY_ESCAPE)
        Cls
        DrawPoly tri
        Flip
Wend

DrawText[edit]

Function DrawText( t$,x#,y# )

Description: Draw text

Information: DrawText prints strings at position x,y of the graphics display using the current image font specified by the SetImageFont command.

Other commands that affect DrawText include SetColor, SetHandle, SetScale, SetRotation, SetOrigin, SetViewPort, SetBlend and SetAlpha.

It is recommended that the blend mode be set to ALPHABLEND using the SetBlend command for non jagged antialiased text. Text that will be drawn at a smaller size using the SetScale command should use fonts loaded with the SMOOTHFONT style to benefit from mip-mapped filtering, see LoadImageFont for more information.

Example:

' drawtext.bmx

' scrolls a large text string across the screen by decrementing the tickerx variable

Graphics 640,480

Local tickerx#=640

text$="Yo to all the Apple, Windows and Linux BlitzMax programmers in the house! "
text:+"Game development is the most fun, most advanced and definitely most cool "
text:+"software programming there is!"

While Not KeyHit(KEY_ESCAPE)
        Cls
        DrawText "Scrolling Text Demo",0,0
        DrawText text,tickerx#,400
        tickerx=tickerx-1
        If tickerx<-TextWidth(text) tickerx=640
        Flip    
Wend

End

DrawImage[edit]

Function DrawImage( image:TImage,x#,y#,frame=0 )

Description: Draw an image to the back buffer

Information: Drawing is affected by the current blend mode, color, scale and rotation.

If the blend mode is ALPHABLEND the image is affected by the current alpha value and images with alpha channels are blended correctly with the background.

DrawImageRect[edit]

Function DrawImageRect( image:TImage,x#,y#,w#,h#,frame=0 )

Description: Draw an image to a rectangular area of the back buffer

Information: Drawing is affected by the current blend mode, color, scale and rotation.

If the blend mode is ALPHABLEND, then the image is also affected by the current alpha value.

TileImage[edit]

Function TileImage( image:TImage,x#=0#,y#=0#,frame=0 )

Description: Draw an image in a tiled pattern

Information: TileImage draws an image in a repeating, tiled pattern, filling the current viewport.

SetColor[edit]

Function SetColor( red,green,blue )

Description: Set current color

Information: The SetColor command affects the color of Plot, DrawRect, DrawLine, DrawText, DrawImage and DrawPoly.

The red, green and blue parameters should be in the range of 0 to 255.

GetColor[edit]

Function GetColor( red Var,green Var,blue Var )

Description: Get red, green and blue component of current color.

Returns: Red, green and blue values in the range 0..255 in the variables supplied.

SetBlend[edit]

Function SetBlend( blend )

Description: Set current blend mode

Information: SetBlend controls how pixels are combined with existing pixels in the back buffer when drawing commands are used in BlitzMax.

blend should be one of:

Blend mode Effect
MASKBLEND Pixels are drawn only if their alpha component is greater than .5
SOLIDBLEND Pixels overwrite existing backbuffer pixels
ALPHABLEND Pixels are alpha blended with existing backbuffer pixels
LIGHTBLEND Pixel colors are added to backbuffer pixel colors, giving a 'lighting' effect
SHADEBLEND Pixel colors are multiplied with backbuffer pixel colors, giving a 'shading' effect

GetBlend[edit]

Function GetBlend()

Description: Get current blend mode

Returns: The current blend mode.

Information: See SetBlend for possible return values.

SetAlpha[edit]

Function SetAlpha( alpha# )

Description: Set current alpha level

Information: alpha should be in the range 0 to 1.

alpha controls the transparency level when the ALPHABLEND blend mode is in effect. The range from 0.0 to 1.0 allows a range of transparency from completely transparent to completely solid.

GetAlpha[edit]

Function GetAlpha#()

Description: Get current alpha setting.

Returns: the current alpha value in the range 0..1.0

SetLineWidth[edit]

Function SetLineWidth( width# )

Description: Sets pixel width of lines drawn with the DrawLine command

GetLineWidth[edit]

Function GetLineWidth#()

Description: Get line width

Returns: Current line width, in pixels

SetMaskColor[edit]

Function SetMaskColor( red,green,blue )

Description: Set current mask color

Information: The current mask color is used to build an alpha mask when images are loaded or modified. The red, green and blue parameters should be in the range of 0 to 255.

GetMaskColor[edit]

Function GetMaskColor( red Var,green Var,blue Var )

Description: Get red, green and blue component of current mask color

Returns: Red, green and blue values in the range 0..255

SetViewport[edit]

Function SetViewport( x,y,width,height )

Description: Set drawing viewport

Information: The current ViewPort defines an area within the back buffer that all drawing is clipped to. Any regions of a DrawCommand that fall outside the current ViewPort are not drawn.

GetViewport[edit]

Function GetViewport( x Var,y Var,width Var,height Var )

Description: Get dimensions of current Viewport.

Returns: The horizontal, vertical, width and height values of the current Viewport in the variables supplied.

SetOrigin[edit]

Function SetOrigin( x#,y# )

Description: Set drawing origin

Information: The current Origin is an x,y coordinate added to all drawing x,y coordinates after any rotation or scaling.

GetOrigin[edit]

Function GetOrigin( x# Var,y# Var )

Description: Get current origin position.

Returns: The horizontal and vertical position of the current origin.

SetHandle[edit]

Function SetHandle( x#,y# )

Description: Set drawing handle

Information: The drawing handle is a 2D offset subtracted from the x,y location of all drawing commands except DrawImage as Images have their own unique handles.

Unlike SetOrigin the drawing handle is subtracted before rotation and scale are applied providing a 'local' origin.

GetHandle[edit]

Function GetHandle( x# Var,y# Var )

Description: Get current drawing handle.

Returns: The horizontal and vertical position of the current drawing handle.

SetRotation[edit]

Function SetRotation( rotation# )

Description: Set current rotation

Information: rotation is given in degrees and should be in the range 0 to 360.

GetRotation[edit]

Function GetRotation#()

Description: Get current Max2D rotation setting.

Returns: The rotation in degrees.

SetScale[edit]

Function SetScale( scale_x#,scale_y# )

Description: Set current scale

Information: scale_x and scale_y multiply the width and height of drawing commands where 0.5 will half the size of the drawing and 2.0 is equivalent to doubling the size.

GetScale[edit]

Function GetScale( scale_x# Var,scale_y# Var )

Description: Get current Max2D scale settings.

Returns: The current x and y scale values in the variables supplied.

SetTransform[edit]

Function SetTransform( rotation#=0,scale_x#=1,scale_y#=1 )

Description: Set current rotation and scale

Information: SetTransform is a shortcut for setting both the rotation and scale parameters in Max2D with a single function call.

LoadImageFont[edit]

Function LoadImageFont:TImageFont( url:Object,size,style=SMOOTHFONT )

Description: Load an image font

Returns: An image font object

Information: style can be a combination of BOLDFONT, ITALICFONT and SMOOTHFONT flags. Use the SMOOTHFONT flag for improved filtering if the font is to be rotated or scaled.

SetImageFont[edit]

Function SetImageFont( font:TImageFont )

Description: Set current image font

Information: In order to DrawText in fonts other than the default system font use the SetImageFont command with a font handle returned by the LoadImageFont command.

Use

SetImageFont Null

to select the default, built-in font.

GetImageFont[edit]

Function GetImageFont:TImageFont()

Description: Get current image font.

Returns: The current image font.

TextWidth[edit]

Function TextWidth( text$ )

Description: Get width of text

Returns: the width, in pixels, of text based on the current image font.

Information: This command is useful for calculating horizontal alignment of text when using the DrawText command.

TextHeight[edit]

Function TextHeight( text$ )

Description: Get height of text

Returns: the height, in pixels, of text based on the current image font.

Information: This command is useful for calculating vertical alignment of text when using the DrawText command.

LoadImage[edit]

Function LoadImage:TImage( url:Object,flags=-1 )

Description: Load an image

Returns: A new image object

Information: url can be either a string or an existing pixmap.

flags can be 0, -1 or any combination of:

Flags value Effect
MASKEDIMAGE The image is masked with the current mask color.
FILTEREDIMAGE The image is smoothed when scaled up to greater than its original

size, when rotated, or when drawn at fractional pixel coordinates.

MIPMAPPEDIMAGE The image is smoothed when scaled down to less than its original size.
DYNAMICIMAGE The image can be modified using LockImage or GrabImage.

Note MIPMAPPEDIMAGE images consume extra video memory, so this flag should only be used when really necessary.

If flags is -1, the auto image flags are used: See AutoImageFlags.

To combine flags, use the | (boolean OR) operator.

LoadAnimImage[edit]

Function LoadAnimImage:TImage( url:Object,cell_width,cell_height,first_cell,cell_count,flags=-1 )

Description: Load a multi-frame image

Returns: An image object

Information: LoadAnimImage extracts multiple image frames from a single, larger image. url can be either a string or an existing pixmap.

See LoadImage for valid flags values.

SetImageHandle[edit]

Function SetImageHandle( image:TImage,x#,y# )

Description: Set an image's handle to an arbitrary point

Information: An image's handle is subtracted from the coordinates of DrawImage before rotation and scale are applied.

AutoMidHandle[edit]

Function AutoMidHandle( enable )

Description: Enable or disable auto midhandle mode

Information: When auto midhandle mode is enabled, all images are automatically 'midhandled' (see MidHandleImage) when they are created. If auto midhandle mode is disabled, images are handled by their top left corner.

AutoMidHandle defaults to False after calling Graphics.

AutoImageFlags[edit]

Function AutoImageFlags( flags )

Description: Set auto image flags

Information: The auto image flags are used by LoadImage and CreateImage when no image flags are specified. See LoadImage for a full list of valid image flags. AutoImageFlags defaults to MASKEDIMAGE | FILTEREDIMAGE.

MidHandleImage[edit]

Function MidHandleImage( image:TImage )

Description: Set an image's handle to its center

ImageWidth[edit]

Function ImageWidth( image:TImage )

Description: Get width of an image

Returns: The width, in pixels, of image

ImageHeight[edit]

Function ImageHeight( image:TImage )

Description: Get height of an image

Returns: The height, in pixels, of image

CreateImage[edit]

Function CreateImage:TImage( width,height,frames=1,flags=-1 )

Description: Create an empty image

Returns: A new image object

Information: CreateImage creates an 'empty' image, which should be initialized using either GrabImage or LockImage before being drawn.

Please refer to LoadImage for valid flags values. The flags value is always combined with DYNAMICIMAGE.

Example:

' createimage.bmx

' creates a 256x1 image with a black to blue color gradient

Const ALPHABITS=$ff000000

Graphics 640,480,32

image=CreateImage(256,1)
map=LockImage(image)
For i=0 To 255
        WritePixel(map,i,0,ALPHABITS|i)
Next
UnlockImage(image)

DrawImageRect image,0,0,640,480
DrawText "Blue Color Gradient",0,0

Flip

WaitKey

LockImage[edit]

Function LockImage:TPixmap( image:TImage,frame=0,read_lock=True,write_lock=True )

Description: Lock an image for direct access

Returns: A pixmap representing the image contents

Information: Locking an image allows you to directly access an image's pixels.

Only images created with the DYNAMICIMAGE flag can be locked.

Locked images must eventually be unlocked with UnlockImage before they can be drawn.

UnlockImage[edit]

Function UnlockImage( image:TImage,frame=0 )

Description: Unlock an image

Information: Unlocks an image previously locked with LockImage.

GrabImage[edit]

Function GrabImage( image:TImage,x,y,frame=0 )

Description: Grab an image from the back buffer

Information: Copies pixels from the back buffer to an image frame.

Only images created with the DYNAMICIMAGE flag can be grabbed.

Example:

' grabimage.bmx

' draws a small graphic then uses grabimage to make an image

' as mask color and cls color both default to black a mask is 
' created for the grabbed where any pixels unset on the backbuffer
' become transparent in the grabbed image

Graphics 640,480

Cls

DrawLine 0,0,32,32
DrawLine 32,0,0,32
DrawOval 0,0,32,32

Local image=CreateImage(640,480,1,DYNAMICIMAGE|MASKEDIMAGE)
GrabImage image,0,0

Cls
For i=1 To 100
        DrawImage image,Rnd(640),Rnd(480)
Next
Flip

WaitKey
 

DrawPixmap[edit]

Function DrawPixmap( pixmap:TPixmap,x,y )

Description: Draw pixmap

GrabPixmap[edit]

Function GrabPixmap:TPixmap( x,y,width,height )

Description: Grab pixmap

ImagesCollide[edit]

Function ImagesCollide(image1:TImage,x1,y1,frame1,image2:TImage,x2,y2,frame2)

Description: Tests if two images collide

Returns: True if any pixels of the two images specified at the given location overlap.

Information: ImagesCollide uses the current Rotation and Scale factors from the most previous call to SetScale and SetRotation to calculate at a pixel level if the two images collide.

ImagesCollide2[edit]

Function ImagesCollide2(image1:TImage,x1,y1,frame1,rot1#,scalex1#,scaley1#,image2:TImage,x2,y2,frame2,rot2#,scalex2#,scaley2#)

Description: Tests if two images with arbitrary Rotation and Scales collide

Returns: True if any pixels of the two images specified at the given location overlap.

Information: ImagesCollide2 uses the specified Rotation and Scale paramteters to calculate at a pixel level if the two images collide (overlap).

ResetCollisions[edit]

Function ResetCollisions(mask%=0)

Description: Clears collision layers specified by the value of mask, mask=0 for all layers.

Information: The BlitzMax 2D collision system manages 32 layers, the mask parameter can be a combination of the following values or the special value COLLISION_LAYER_ALL in order to perform collision operations on multiple layers.

Note: COLLISION_LAYER_32 is used by the ImagesCollide and ImagesCollide2 commands.

Layer Mask value
COLLISION_LAYER_ALL 0
COLLISION_LAYER_1 $0001
COLLISION_LAYER_2 $0002
COLLISION_LAYER_3 $0004
COLLISION_LAYER_4 $0008
COLLISION_LAYER_5 $0010
COLLISION_LAYER_6 $0020
COLLISION_LAYER_7 $0040
COLLISION_LAYER_8 $0080
COLLISION_LAYER_9 $0100
COLLISION_LAYER_10 $0200
COLLISION_LAYER_11 $0400
COLLISION_LAYER_12 $0800
COLLISION_LAYER_13 $1000
COLLISION_LAYER_14 $2000
COLLISION_LAYER_15 $4000
COLLISION_LAYER_16 $8000

CollideImage[edit]

Function CollideImage:Object[](image:TImage,x,y,frame,collidemask%,writemask%,id:Object=Null)

Description: Pixel accurate collision testing between transformed Images.

Information: The collidemask specifies any layers to test for collision with.

The writemask specifies which if any collision layers the image is added to in its currently transformed state.

The id specifies an object to be returned to future CollideImage calls when collisions occur.

Example:

Strict

Local rot,x,y

Graphics 640,480

AutoMidHandle True      'image will rotate around it's center

Local image:TImage=LoadImage("bullet.png")

While Not KeyHit(KEY_ESCAPE)
        Cls
        ResetCollisions

' draw the first image at 5 times the size and on an arbitrary angle
        
        SetScale 5,5
        SetRotation 125

        DrawImage image,200,200

' add the first image to the first collision layer at same postion, rotation 
' and scale as it has just been drawn

        CollideImage image,200,200,0,0,1

' move the other image relative to the mouse and rotate it continuously

        x=MouseX()
        y=MouseY()-20
        rot:+1

        SetRotation rot
        DrawImage image,x,y

' test the image at it's current rotation, scale and position with images
' that have been added to the first collision layer

        If CollideImage(image,x,y,0,1,0)

' reset scale and rotation states so our text is drawn correctly                

                SetScale 1,1
                SetRotation 0
                DrawText "COLLISION!",20,20

        EndIf

        Flip
Wend

CollideRect[edit]

Function CollideRect:Object[](x,y,w,h,collidemask%,writemask%,id:Object=Null)

Description: Pixel accurate collision testing between image layers

Information: The collidemask specifies any layers to test for collision with.

The writemask specifies which if any collision layers the image is added to in its currently transformed state.

The id specifies an object to be returned to future CollideImage calls when collisions occur.