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Return an Indexed8 QImage

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Ensures it'll be encoded as such when saved as a PNG
This commit is contained in:
NiLuJe 2019-05-24 01:14:47 +02:00
parent 7e6347486b
commit 90ab7573d9
2 changed files with 13 additions and 7 deletions
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12
src/calibre/utils/imageops/ordered_dither.cpp
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@ -70,9 +70,9 @@ static uint8_t
QImage ordered_dither(const QImage &image) { // {{{
ScopedGILRelease PyGILRelease;
QImage img = image;
QRgb *row = NULL, *pixel = NULL;
int y = 0, x = 0, width = img.width(), height = img.height();
uint8_t gray = 0, dithered = 0;
QImage dst(width, height, QImage::Format_Indexed8);
// We're running behind blend_image, so, we should only ever be fed RGB32 as input...
if (img.format() != QImage::Format_RGB32) {
@ -81,13 +81,15 @@ QImage ordered_dither(const QImage &image) { // {{{
}
for (y = 0; y < height; y++) {
row = reinterpret_cast<QRgb*>(img.scanLine(y));
for (x = 0, pixel = row; x < width; x++, pixel++) {
const QRgb *src_row = reinterpret_cast<const QRgb*>(img.constScanLine(y));
uint8_t *dst_row = dst.scanLine(r);
for (x = 0; x < width; x++) {
const QRgb pixel = *(src_row + x);
// We're running behind grayscale_image, so R = G = B
gray = qRed(*pixel);
dithered = dither_o8x8(x, y, gray);
*pixel = qRgb(dithered, dithered, dithered);
*(dst_row + x) = dithered;
}
}
return img;
return dst;
} // }}}

8
src/calibre/utils/img.py
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@ -463,10 +463,14 @@ def quantize_image(img, max_colors=256, dither=True, palette=''):
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.
Returns a QImage in Indexed8 pixel format.
'''
img = image_from_data(img)
if img.hasAlphaChannel():
img = blend_image(img)
return imageops.ordered_dither(img)
# }}}