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Diffstat (limited to 'vendor/x11iraf/obm/ObmW/Notes')
| -rw-r--r-- | vendor/x11iraf/obm/ObmW/Notes | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/vendor/x11iraf/obm/ObmW/Notes b/vendor/x11iraf/obm/ObmW/Notes new file mode 100644 index 00000000..fe635b21 --- /dev/null +++ b/vendor/x11iraf/obm/ObmW/Notes @@ -0,0 +1,191 @@ + GUI WORK NOTES - November 1993 + +TODO + + enhance mapping code in Gterm widget (see below) + ximtool enhancements + locator, magnifier, control panel, socket support, etc. + clean up xgterm + - beta release - + obm enhancements + more gui bindings, new widgets + imbrowse, movie demos + obm documentation + + +1. MAPPINGS + + src rect -> dst rect + + construct pixel level mappings for each axis + this source pixel maps to these destination pixels + this destination pixel maps to these source pixels + + in general (zoom/dezoom) the mapping is not one-to-one + when one source pixel maps to several destination pixels, pixel replication + is used to draw the destination pixels + when one destination pixel maps to several source pixels the destination + pixel value may be computed by any of several different techniques + + major cases + + mapping is one-to-one + mapping is one-to-many zoom mapping (pixel replication) + mapping is many-to-one dezoom mapping (antialias) + + antialiasing techniques + + nearest nearest neighbor + bilinear 2x2 distance weighted sum + + area included area weighted sum + lowpass convolve followed by nearest neighbor + gaussian gaussian weighted sum over NxN pixels + + All of these involve projecting the center of each destination + pixel back into the source raster. The antialiasing technique + applied to the NxN neighborhood around the source coordinate + then determines the value of the destination pixel. + + Reasonable choices + nearest fastest, but no antialiasing + bilinear mininum smoothing if mag < 2 + lowpass not bad for mag < 3 + area,gaussian best for large demagnification ratios + + Nearest and bilinear (NB) are mutually exclusive and may be selected + independently of area, lowpass, or gaussian (ALG). If one of ALG is + selected and one of NB is also selected, the antialias code will use + one or the other technique depending upon the scaling. If one of NB + or ALG is selected but not both, the specified technique will be + used regardless of the scaling. + + setMapping should compute scaling maps + copyRaster uses these to compute the destination pixels + refreshRaster uses these to compute region of source rect + + computing a mapping + rasterop + src rect, dst rect + coordinate types + flags: enabled, defined, refresh + scaling type (unitary, zoom, dezoom) + backprojection array maps dst pixel to src pixel + integer mapping (1-1, zoom): pixel number, integer + antialias mapping (dezoom): pixel center, floating + extent array gives range of dst pixels affected by a given + src pixel - 2 values per source pixel + xscale, yscale (forward direction) + + +2. PSEUDOCODE + +procedure copyRaster (src, src rect, dst, dst rect) +begin + create temporary mapping + refresh entire mapping +end + +procedure writePixels (dst, dst rect, pixels) +begin + modify source raster pixels + update any mappings that intersect source rect +end + +procedure setMapping (mapping, mapping data) +begin + if (new mapping, mapping not enabled, or refreshNone set) + merely store new mapping + else { + # Edit and refresh a mapping. + if (scale is unchanged) { + compare old, new mappings + refresh only changed regions + store new mapping + } else { + store new mapping + refresh entire mapping + } + refresh any uncovered regions + } + + if (mapping is one-to-one) { + scaling = none + } else if (mapping is one-to-many) { + compute integer dst->src scaling maps + scaling = zoom + } else if (mapping is many-to-one) { + compute array of back projected dst->src pixel centers + scaling = dezoom + } +end + +procedure refresh_source (mapping, source rect) +begin + compute destination rect + refresh_destination (mapping, destination rect) +end + +procedure refresh_destination (mapping, destination rect) +begin + set clip mask in GC to prevent drawing into any mapped regions + which cover the mapping being refreshed + + # Special case of pixmap to pixmap copy with no scaling. + if (no scaling and src is pixmap and dst is pixmap) { + do direct XCopyArea + goto done + } + + # Get source ximage. + if (src is pixmap) { + xin = ximage returned by XGetImage + set del_xin flag + } else + xin = src ximage + + # Special case of ximage to pixmap copy with no scaling. + if (no scaling and dst is pixmap) { + do XPutImage to write xin to dst pixmap + goto done + } + + # Get destination ximage. + if (dst is pixmap) { + xout = create an ximage of the required size + set del_xout flag + } else + xout = dst ximage + + # Copy src ximage to dst ximage. + if (mapping is one to one) { + copy region of xin to xout without scaling + + } else if (mapping is one to many - zoom) { + for (each line of destination) + if (mapped src Y same as previous line) + copy previous dst line + else { + for (each destination pixel) + pixel = get pixel from xin using dst->src map + } + + } else (mapping is many to one - dezoom) { + if (function is lowpass) { + compute lowpass xin + set function to nearest neighbor + } + + for (each line of destination) + for (each destination pixel) + pixel = antialias_function (src, x, y, nx, ny) + } + + if (dst is pixmap) + do XPutImage to write xout to dst pixmap + + clear clip mask in GC +end + + + |