Defined in Image.Def Inherits from Linkable Inherits Interface from Pixels, HasDigest
Most viewable objects, including stamps, buttons, and gadgets, use a bitmap to describe their appearance on the screen. These bitmaps are instances of class Image. Image objects include other information that's used when drawing the objects they're associated with, such as the image's size and center point.
Version note: This chapter is under construction. Watch out for falling girders. Use caution. And take the following advice to heart:
Remember that if the documentation and the software (especially the definition files) disagree, always trust the software.
Most viewables include a reference to an object of class Image that defines the object's appearance. When you create one of these viewables, you'll specify the image to be used by the viewable. Image objects consist of bitmaps with additional supporting information.
You can put a new image into the Macintosh-resident version of Magic Cap by using standard Macintosh copy and paste, like this:
Every viewable that uses an image displays its image in an image coupon when you tinker with it. You can apply one viewable's image to another by tinkering with the first viewable, dragging its image coupon out of the tinkering window, closing the tinkering window, then dragging the image coupon to the desired viewable and dropping it in.
You can also connect a viewable to an image in your package's instance definition file. Every viewable that uses an image has an image field to refer to it. To make the viewable use a particular image, just put that image in the viewable's image field in your instance definition file.
When you see an image in an instance definition file, you'll find that most of the definition is taken up by data that describes the image's bitmap. This information looks daunting, but it's generated automatically by ObjectMaker when you decompile your objects to text, so you'll never have to construct it yourself.
Magic Cap includes many images that you can use. These images are defined as indexicals, which gives you access to them from your package. For example, indexical {6,53} is a birthday card image. For a complete list of indexical images you can use, as well as all other indexicals, see the Indexicals.h file, especially list 6.
Instantiate: sometimes Subclass: rarely Call its methods: rarely
You'll create objects of class Image if you ever paste images into the Macintosh-based version of Magic Cap. You can see the text description of these images when you decompile objects with ObjectMaker. You'll probably never create a text description of an image yourself, although you might modify an image description created by ObjectMaker.
The Image class has the following methods you might call:
| Method | Description |
|---|---|
| image geometry | |
| Thickness | Return the size of the image relative to the origin |
| BorderThickness | Return the thickness of the border around content; always returns 0; override to implement borders |
| RepeatThickness | Thickness of repeat area within border; always returns 0; override to change |
| ImageBoundsBox | Determine a bounding box for the image, centered on the supplied position dot |
| ImageBoundsBoxRotated | Determine a bounding box for the image given a rotation |
| ImageContentBox | Always empty; override to change |
| ImageBoundsDot | |
| Drawing the image | |
| DrawImageScaled | Draw the image with the given modifications | DrawImageInBox | DrawImageRotated | DrawImageRotatedColored | DrawImagedRotatedShadow |
| DrawBorder | Draw the image's border |
| DrawComplexBorderShadow | |
| Manipulating the image | |
| ChangeImage | Replace the image with a new image, in the same object, setting flags appropriately |
| FinePointing | Returns the value of the flag imagefinepointingbit |
| SetFinePointing | Sets the imagefinepointingbit to the given boolean |
| ShrinkImage | Shrink the image <<how much?>> |
Whenever you create a subclass of the Image class, you should override the following methods:
| Method | Description |
|---|---|
| DrawImage | Draw the image |
The Image class defines the following fields:
| Field | Type | Description |
|---|---|---|
| Inherited from SingleLinkable: | ||
| next | Object | Next item in list |
| Inherited from Linkable: | ||
| previous | Object | Previous item in list |
| Defined by Image: | ||
| imageFlags | Unsigned | Various flags for image |
| imageSize | PixelDot | Size of image in pixels |
| resolution | UnsignedShort | Microns per bit ?? |
| depth | UnsignedShort | Bits per pixel of image |
| centerPt | PixelDot | Center of image in pixels |
| crc32 | Unsigned | Computed checksum of image |
The bitmap for an image is contained in the variable-length data at the end of the object, not in any of the object's fields.
#define rectImageBit31 #define rectImageMask0x80000000
This flag is set if the image is rectangular.
#define hasMaskBit30 #define hasMaskMask0x40000000
This flag is set if mask data is appended to the image.
#define allBlackBit29 #define allBlackMask0x20000000
This bit is set if the image is all black.
#define containsNameBit28 #define containsNameMask0x10000000
Set this flag if the image displays its own name, so a label would be unecessary.
#define packedBit23 #define packedMask0x00800000
This flag is true if the image data has been packed with PackBytes.
#define aligned32Bit22 #define aligned32Mask0x00400000
This flag is true if rowBytes is a multiple of 4 bytes.
#define imageFinePointingBit21 #define imageFinePointingMask0x00200000
Set this flag if the system should use the image mask for hit-testing this image.
/* bits of orientation */ #define rotateBit 2 #define hFlipBit 1 #define vFlipBit 0 /* image orientation bitMasks */ #define rotateMask (1 << rotateBit) #define hFlipMask (1 << hFlipBit) #define vFlipMask (1 << vFlipBit)
operation GetThickness(VAR thickness: Box) call: sometimes Override: rarely
Call GetThickness to return the width and height of the image in microns.