logiBITBLT - What 2D operations are supported by logiBITBLT
What 2D operations are supported by logiBITBLT?

2D operations supported by logiBITBLT are:

1. Move operation - The bitmap stored in one area of the memory is tranferred to another area. Move operation is performed without image artefacts due to overlapping parts of the old image. Move in positive and negative direction is supported.

2. Raster operation  (ROP2) - Boolean logic operations between source and destination pixels as operands are available. Source and destination pixels can be logically combined (AND, OR, XOR, NOR, or combination of these logic operations) into a resulting value stored into destination bitmap.

3. Pattern fill - Pattern fill operation fills destination bitmap with predefined 8x8 pixels pattern. Starting pixel of the pattern can be programmed in order to get different fill efects.

4. Solid fill - Solid fill destination area of the memory with any color format that is supported in logiBITBLT. Color used for solid fill is set in background color register - BG_COL_REG.

5. Color expansion - The color expansion operation is commonly used for color font creation or an overlay creation. A monochromatic bitmap is expanded with background and foreground color (BG_COL_REG and FG_COL_REG registers). Each monochromatic bitmap pixel is tranferred to the destination bitmap as a color pixel. The monochromatic pixel value determines between destination pixel foreground or background color.

6. Anti-aliased 8-bit font expansion - Anti-aliased (AA) 8-bit font expansion operation is used to generate anti-aliased fonts. Fonts are stored in memory in 8 bpp format. Each 8-bit value is expanded to corresponded 32-bit value (ARGB) stored in AA_FONT_COLOR_RAM located in logiBITBLT register module. Value inside RAM is given in ARGB format: ARGB6565 or ARGB8888.

7. Porter-Duff composition - Porter-Duff composing technique is used for anti-aliasing accumulation of the full bitmap. It composites each object (source) onto the background bitmap (destination), that has an effect of overlaying the object over the background. Where the objects overlap and coverage is not complete, the color of the background may show through the object that has just been rendered.

8. RLE decompression - The RLE compression is used for bitmap storage. logiBITBLT decompresses source bitmap with Run-Length Encoding. Run-Length Encoding (RLE) is a data compression algorithm where a long sequence of the 32-bit data is replaced by a shorter sequence, two 32-bit words containing a length information and repeated 32-bit data. For the short sequence RLE is not optimal, so escape sequence is used. If the length information is negative next sequence is not compressed.

9. Color-keyed transparency - One of the most used logiBITBLT features is a transparency operation. The source bitmap is conditionally transferred to the destination bitmap. Some pixels in the destination bitmap area (rectangle) keep the destination pixel value, while others are assigned by source pixel values (color). logiBITBLT uses color-keyed transparency operation method. One color in the source bitmap is declared the transparency key. Whenever this color occures in the source bitmap, the source pixel is not transferred to the destination bitmap. Instead this destination bitmap pixel remains unaltered. The background color register (BG_COL_REG) is used as a color key setup for the transparent operations.

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