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Add trim option to provide a specific background colour (#3332)

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Co-authored-by: Mart Jansink <mart@cinemait.nl>
This commit is contained in:
Mart
2022-08-23 13:28:02 +02:00
committed by GitHub
parent 3a44748f49
commit c3a852eecf
14 changed files with 240 additions and 45 deletions
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32
src/operations.cc
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@@ -262,26 +262,42 @@ namespace sharp {
/*
Trim an image
*/
VImage Trim(VImage image, double const threshold) {
VImage Trim(VImage image, std::vector<double> background, double threshold) {
if (image.width() < 3 && image.height() < 3) {
throw VError("Image to trim must be at least 3x3 pixels");
}
// Top-left pixel provides the background colour
VImage background = image.extract_area(0, 0, 1, 1);
if (HasAlpha(background)) {
background = background.flatten();
// Scale up 8-bit values to match 16-bit input image
double multiplier = sharp::Is16Bit(image.interpretation()) ? 256.0 : 1.0;
threshold *= multiplier;
std::vector<double> backgroundAlpha(1);
if (background.size() == 0) {
// Top-left pixel provides the default background colour if none is given
background = image.extract_area(0, 0, 1, 1)(0, 0);
multiplier = 1.0;
}
if (background.size() == 4) {
// Just discard the alpha because flattening the background colour with
// itself (effectively what find_trim() does) gives the same result
backgroundAlpha[0] = background[3] * multiplier;
}
background = {
background[0] * multiplier,
background[1] * multiplier,
background[2] * multiplier
};
int left, top, width, height;
left = image.find_trim(&top, &width, &height, VImage::option()
->set("background", background(0, 0))
->set("background", background)
->set("threshold", threshold));
if (HasAlpha(image)) {
// Search alpha channel (A)
int leftA, topA, widthA, heightA;
VImage alpha = image[image.bands() - 1];
VImage backgroundAlpha = alpha.extract_area(0, 0, 1, 1);
leftA = alpha.find_trim(&topA, &widthA, &heightA, VImage::option()
->set("background", backgroundAlpha(0, 0))
->set("background", backgroundAlpha)
->set("threshold", threshold));
if (widthA > 0 && heightA > 0) {
if (width > 0 && height > 0) {