<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd"> <html><head><meta name="qrichtext" content="1" /><style type="text/css"> p, li { white-space: pre-wrap; } </style></head><body style=" font-family:'Terminus'; font-size:9pt; font-weight:400; font-style:normal;"> On Thursday 10 February 2011 21:08:33 Bill Spitzak wrote: > It sounds to me like you are proposing that a binary zero-or-source > decision be made for each pixel in the output space. I don't think this > will work. Something like this (decision about which pixels in the output space correspond to the zero padding source pixels) is done in 'pad_repeat_get_scanline_bounds' function here for the nearest scaling: http://cgit.freedesktop.org/pixman/tree/pixman/pixman-fast-path.h?id=pixman-0.21.4#n61 This function could be also used for Y axis to skip whole top/bottom padding scanlines. If I understand it correctly, Soeren suggests moving/duplicating this or similar logic into some common code which would run before fast paths and shrink the output region if possible. > The pixel sampling of the source needs to do this, otherwise filtering > cannot be used to produce an antialiased edge where the image > transitions to NONE. The discussed patch deals with the nearest filter only, so antialiased edges are not involved there. Anyway, right now I'm actually working on a similar function specifically for bilinear scaling, which would detect 5 zones: left-padding, transition-zone, only image, transition-zone, right-padding When handling the pixels exclusively from the image itself, bilinear scanline processing code can run at full speed. Left padding and right padding for NONE repeat can be handled in a similar way as for nearest scaling (we can provide source top/bottom scanline pointers pointing to a small zero filled buffer and set 'unit_x' parameter to 0 in order to prevent it from advancing forward). Transition zones are going to be a bit more tricky because a single extra boolean hint argument will not help, and probably some kind of additional optional mask buffers will be required to be passed to the scanline processing function. But I want to implement fast SIMD optimized bilinear scaling only for a8r8g8b8/x8r8g8b8/r5g6b5 formats, SRC operator and PAD repeat first. So I'm just going to ignore NONE repeat related issues initially :) And in the case of bilinear scaling, left-padding and right-padding zones could be removed from the output region too. -- Siarhei > Soeren Sandmann wrote: > > Siarhei Siamashka <siarhei.siamashka@gmail.com> writes: > >> From: Siarhei Siamashka <siarhei.siamashka@nokia.com> > >> > >> Scaling function now gets an extra boolean argument, which is set > >> to TRUE when we are fetching padding pixels for NONE repeat. This > >> allows to make a decision whether to interpret alpha as 0xFF or 0x00 > >> for such pixels when working with formats which don't have alpha > >> channel (for example x8r8g8b8 and r5g6b5). > > > > Another way to do this would be to clip away zeros up front for source > > images. For example, a new function pointer could be added to the > > > > image struct: > > clip_zeros (pixman_image_t *image, pixman_region_t *region) > > > > that would clip away those parts of region where the image is known to > > be zero. Then, in pixman.c, this function could be called for both > > source and mask if the operator was one where zeros had no effect. > > > > That would benefit all operations and avoid cluttering these > > macros. It would also cause the SAMPLES_COVER_CLIP to be set in more > > cases. > > > > I'm fine with this patch as is too though. > > > > > > Soren </body></html>