From 67b383835743e496848ad38304ed73df2a8f1201 Mon Sep 17 00:00:00 2001
From: Manuel Gunther <siebenkopf@googlemail.com>
Date: Tue, 26 Jul 2016 16:12:53 -0600
Subject: [PATCH] Properly handled alpha channels by having png ignoring it;
added support for gray+alpha
---
bob/io/image/cpp/png.cpp | 63 ++++++++++++++++++----------------------
1 file changed, 28 insertions(+), 35 deletions(-)
diff --git a/bob/io/image/cpp/png.cpp b/bob/io/image/cpp/png.cpp
index 54d6724..75e244b 100644
--- a/bob/io/image/cpp/png.cpp
+++ b/bob/io/image/cpp/png.cpp
@@ -99,13 +99,7 @@ static void im_peek(const std::string& path, bob::io::base::array::typeinfo& inf
// Set depth and number of dimensions
info.dtype = (bit_depth <= 8 ? bob::io::base::array::t_uint8 : bob::io::base::array::t_uint16);
- if(color_type == PNG_COLOR_TYPE_GRAY)
- info.nd = 2;
- else if (color_type == PNG_COLOR_TYPE_RGB || PNG_COLOR_TYPE_RGB_ALPHA || PNG_COLOR_TYPE_PALETTE)
- info.nd = 3;
- else {// Unsupported color type
- throw std::runtime_error("PNG: codec does not support images with color spaces different than GRAY, RGB, RGBA or Indexed colors (Palette)");
- }
+ info.nd = color_type & PNG_COLOR_MASK_COLOR ? 3 : 2;
if(info.nd == 2)
{
info.shape[0] = height;
@@ -149,18 +143,18 @@ void im_load_gray(png_structp png_ptr, bob::io::base::array::interface& b)
}
template <typename T> static
-void imbuffer_to_rgb(const size_t size, const T* im, T* r, T* g, T* b, const size_t number_of_elements)
+void imbuffer_to_rgb(const size_t size, const T* im, T* r, T* g, T* b)
{
for(size_t k=0; k<size; ++k)
{
- r[k] = im[number_of_elements*k];
- g[k] = im[number_of_elements*k +1];
- b[k] = im[number_of_elements*k +2];
+ *r++ = *im++;
+ *g++ = *im++;
+ *b++ = *im++;
}
}
template <typename T> static
-void im_load_color(png_structp png_ptr, bob::io::base::array::interface& b, bool has_alpha)
+void im_load_color(png_structp png_ptr, bob::io::base::array::interface& b)
{
const bob::io::base::array::typeinfo& info = b.type();
const size_t height = info.shape[1];
@@ -168,10 +162,8 @@ void im_load_color(png_structp png_ptr, bob::io::base::array::interface& b, bool
const size_t frame_size = height * width;
const size_t row_color_stride = width;
- const size_t number_of_elements = has_alpha ? 4 : 3;
-
// Allocate array to contains a row of RGB-like pixels
- boost::shared_array<T> row(new T[number_of_elements*width]);
+ boost::shared_array<T> row(new T[3*width]);
png_bytep row_pointer = reinterpret_cast<png_bytep>(row.get());
#ifdef PNG_READ_INTERLACING_SUPPORTED
@@ -195,7 +187,7 @@ void im_load_color(png_structp png_ptr, bob::io::base::array::interface& b, bool
for(size_t y=0; y<height; ++y)
{
png_read_row(png_ptr, row_pointer, NULL);
- imbuffer_to_rgb(row_color_stride, reinterpret_cast<T*>(row_pointer), element_r, element_g, element_b, number_of_elements);
+ imbuffer_to_rgb(row_color_stride, reinterpret_cast<T*>(row_pointer), element_r, element_g, element_b);
element_r += row_color_stride;
element_g += row_color_stride;
element_b += row_color_stride;
@@ -256,27 +248,28 @@ static void im_load(const std::string& filename, bob::io::base::array::interface
png_set_expand_gray_1_2_4_to_8(png_ptr);
else if(color_type == PNG_COLOR_TYPE_PALETTE)
png_set_palette_to_rgb(png_ptr);
-
- // We currently only support grayscale and rgb images
- if(color_type != PNG_COLOR_TYPE_GRAY &&
- color_type != PNG_COLOR_TYPE_RGB &&
- color_type != PNG_COLOR_TYPE_PALETTE &&
- color_type != PNG_COLOR_TYPE_RGB_ALPHA) {
- throw std::runtime_error("PNG: codec does not support images with color spaces different than GRAY, RGB, RGBA or Indexed colors (Palette)");
+ // skip the alpha channel
+ if ((color_type & PNG_COLOR_MASK_ALPHA) || png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
+ png_set_strip_alpha(png_ptr);
+
+ // Check color type
+ switch (color_type){
+ // I think that should be all, but in case a new version comes up with a different color space...
+ case PNG_COLOR_TYPE_GRAY:
+ case PNG_COLOR_TYPE_GRAY_ALPHA:
+ case PNG_COLOR_TYPE_RGB:
+ case PNG_COLOR_TYPE_PALETTE:
+ case PNG_COLOR_TYPE_RGB_ALPHA:
+ break;
+ default:
+ throw std::runtime_error("PNG: codec does not support images with color spaces different than GRAY, GRAY+alpha, RGB, RGB+alpha or Indexed colors (Palette)");
}
// 7. Read content
const bob::io::base::array::typeinfo& info = b.type();
- bool has_alpha = (color_type & PNG_COLOR_MASK_ALPHA) == PNG_COLOR_MASK_ALPHA;
- // Handle tRNS color type
- if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)){
- // old tRNS structure, with 8 bit palette including alpha channel
- png_set_tRNS_to_alpha(png_ptr);
- has_alpha = true;
- }
if(info.dtype == bob::io::base::array::t_uint8) {
if(info.nd == 2) im_load_gray<uint8_t>(png_ptr, b);
- else if( info.nd == 3) im_load_color<uint8_t>(png_ptr, b, has_alpha);
+ else if(info.nd == 3) im_load_color<uint8_t>(png_ptr, b);
else {
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
boost::format m("the image in file `%s' has a number of dimensions for which this png codec has no support for: %s");
@@ -286,7 +279,7 @@ static void im_load(const std::string& filename, bob::io::base::array::interface
}
else if(info.dtype == bob::io::base::array::t_uint16) {
if(info.nd == 2) im_load_gray<uint16_t>(png_ptr, b);
- else if( info.nd == 3) im_load_color<uint16_t>(png_ptr, b, has_alpha);
+ else if( info.nd == 3) im_load_color<uint16_t>(png_ptr, b);
else {
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
boost::format m("the image in file `%s' has a number of dimensions for which this png codec has no support for: %s");
@@ -335,9 +328,9 @@ void rgb_to_imbuffer(const size_t size, const T* r, const T* g, const T* b, T* i
{
for (size_t k=0; k<size; ++k)
{
- im[3*k] = r[k];
- im[3*k+1] = g[k];
- im[3*k+2] = b[k];
+ *im++ = *r++;
+ *im++ = *g++;
+ *im++ = *b++;
}
}
--
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