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Inline the grayscaling pass in ordered_dither

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Saving one QImage pixel-loop dance in the process...
This commit is contained in:
NiLuJe 2019-05-24 20:06:51 +02:00
parent 4326bb9d7f
commit 8e7b519b8d
2 changed files with 12 additions and 6 deletions
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8
src/calibre/utils/imageops/ordered_dither.cpp
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@ -109,13 +109,19 @@ QImage ordered_dither(const QImage &image) { // {{{
if (img.isNull()) throw std::bad_alloc();
}
const bool is_gray = img.isGrayscale();
for (y = 0; y < height; y++) {
const QRgb *src_row = reinterpret_cast<const QRgb*>(img.constScanLine(y));
uint8_t *dst_row = dst.scanLine(y);
for (x = 0; x < width; x++) {
const QRgb pixel = *(src_row + x);
// We're running behind grayscale_image, so R = G = B
if (is_gray) {
// Grayscale and RGB32, so R = G = B
gray = qRed(pixel);
} else {
gray = qGray(pixel);
}
dithered = dither_o8x8(x, y, gray);
*(dst_row + x) = dithered; // ... or palette.indexOf(dithered); for Indexed8
}

8
src/calibre/utils/img.py
View File

@ -227,7 +227,7 @@ def save_cover_data_to(data, path=None, bgcolor='#ffffff', resize_to=None, compr
if img.hasAlphaChannel():
changed = True
img = blend_image(img, bgcolor)
if grayscale:
if grayscale and not eink:
if not img.allGray():
changed = True
img = grayscale_image(img)
@ -464,13 +464,13 @@ def eink_dither_image(img):
''' Dither the source image down to the eInk palette of 16 shades of grey,
using ImageMagick's OrderedDither algorithm.
NOTE: Expects input as a grayscale image in RGB32 pixel format (as returned by grayscale_image).
Running blend_image if the image has an alpha channel,
or grayscale_image if it's not already grayscaled is the caller's responsibility.
NOTE: No need to call grayscale_image first, as this will inline a grayscaling pass if need be.
Returns a QImage in Grayscale8 pixel format.
'''
img = image_from_data(img)
if img.hasAlphaChannel():
img = blend_image(img)
return imageops.ordered_dither(img)
# }}}