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Gecko:Image Snapping and Rendering: Difference between revisions
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Gecko:Image Snapping and Rendering (view source)
Revision as of 03:36, 4 October 2008
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# The device pixels that are filled should be the logical fill rectangle rounded to device pixel edges, preserving device pixel centers. (RATIONALE: That's how we "pixel snap" solid rect fills and image drawing should be consistent with solid fills in the pixels that are touched. Satisfies Principles #2 and #3.) | # The device pixels that are filled should be the logical fill rectangle rounded to device pixel edges, preserving device pixel centers. (RATIONALE: That's how we "pixel snap" solid rect fills and image drawing should be consistent with solid fills in the pixels that are touched. Satisfies Principles #2 and #3.) | ||
# Every image pixel sampled in actual rendering would also be sampled by an ideal rendering to an infinite-resolution device. (RATIONALE: Web authors should not be faced with fringes contributed by pixels they did not intend to be sampled.) | # Every image pixel sampled in actual rendering would also be sampled by an ideal rendering to an infinite-resolution device. (RATIONALE: Web authors should not be faced with fringes contributed by pixels they did not intend to be sampled.) | ||
# If the initial rectangle size in device pixels equals the image size in CSS pixels, then the filled area is rendered as a simple copy of the ideal rendering translated by less than or equal to | # If the initial rectangle size in device pixels equals the image size in CSS pixels, then the filled area is rendered as a simple copy of the ideal rendering translated by less than or equal to half a pixel in the horizontal and vertical directions (except where the ideal rendering has only partial pixels, in which case the rendering is not constrained by this requirement). (RATIONALE: If the scale factor in the author's design is exactly the inverse of the scale required by the device, we must avoid scaling and subpixel translation or there will be unnecessary image blurring and performance penalty; in fact, all we're allowed to do is translate the rendering by a minimal amount to pixel-align the image.) | ||