Use preview when available in the header #4

afichet · May 27, 2021 · 09a4445 · 09a4445
1 parent f287e01
commit 09a4445
Showing 1 changed file with 56 additions and 32 deletions.
diff --git a/src/openexr-thumbnailer.cpp b/src/openexr-thumbnailer.cpp
@@ -15,10 +15,13 @@
 #include <OpenEXR/ImfRgbaFile.h>
 #include <OpenEXR/ImfArray.h>
 #include <OpenEXR/ImfHeader.h>
+#include <OpenEXR/ImfPreviewImage.h>
 #include <OpenEXR/ImfChromaticitiesAttribute.h>
 
 #include <cmath>
 
+#define USE_PREVIEW
+
 double to_sRGB(double rgb_color)
 {
     const double a = 0.055;
@@ -30,50 +33,68 @@ double to_sRGB(double rgb_color)
 
 unsigned char *load_exr(const char *path, int *width, int *height)
 {
-    // MyStream stream(buffer, size, "test");
-    Imf::Array2D<Imf::Rgba> pixels;
-
     Imf::RgbaInputFile f(path);
-    Imath::Box2i       dw = f.dataWindow();
-    int                w  = dw.max.x - dw.min.x + 1;
-    int                h  = dw.max.y - dw.min.y + 1;
-    *width                = w;
-    *height               = h;
+    unsigned char *img = nullptr;
+
+#ifdef USE_PREVIEW
+    if (f.header().hasPreviewImage()) {
+        const Imf::PreviewImage &preview = f.header().previewImage();
+        *width  = preview.width();
+        *height = preview.height();
+        img     = new unsigned char[3 * (*width) * (*height)];
+
+        for (int i = 0; i < (*width) * (*height); i++) {
+            img[3*i + 0] = preview.pixels()[i].r;
+            img[3*i + 1] = preview.pixels()[i].g;
+            img[3*i + 2] = preview.pixels()[i].b;
+        }
+    } else {
+#endif // USE_PREVIEW
+        Imf::Array2D<Imf::Rgba> pixels;
 
-    pixels.resizeErase(h, w);
-    f.setFrameBuffer(&pixels[0][0] - dw.min.x - dw.min.y * w, 1, w);
-    f.readPixels(dw.min.y, dw.max.y);
+        Imath::Box2i       dw = f.dataWindow();
+        int                w  = dw.max.x - dw.min.x + 1;
+        int                h  = dw.max.y - dw.min.y + 1;
+        *width                = w;
+        *height               = h;
+        img                   = new unsigned char[3 * w * h];
 
-    // Check if there is specific chromaticities tied to the color representation in this part.
-    const Imf::ChromaticitiesAttribute *c = f.header().findTypedAttribute<Imf::ChromaticitiesAttribute>("chromaticities");
+        pixels.resizeErase(h, w);
+        f.setFrameBuffer(&pixels[0][0] - dw.min.x - dw.min.y * w, 1, w);
+        f.readPixels(dw.min.y, dw.max.y);
 
-    Imf::Chromaticities chromaticities;
+        // Check if there is specific chromaticities tied to the color representation in this part.
+        const Imf::ChromaticitiesAttribute *c = f.header().findTypedAttribute<Imf::ChromaticitiesAttribute>("chromaticities");
 
-    if (c != nullptr) {
-        chromaticities = c->value();
-    }
+        Imf::Chromaticities chromaticities;
 
-    // Handle custom chromaticities
-    Imath::M44f RGB_XYZ = Imf::RGBtoXYZ(chromaticities, 1.f);
-    Imath::M44f XYZ_RGB = Imf::XYZtoRGB(Imf::Chromaticities(), 1.f);
+        if (c != nullptr) {
+            chromaticities = c->value();
+        }
+
+        // Handle custom chromaticities
+        Imath::M44f RGB_XYZ = Imf::RGBtoXYZ(chromaticities, 1.f);
+        Imath::M44f XYZ_RGB = Imf::XYZtoRGB(Imf::Chromaticities(), 1.f);
 
-    Imath::M44f conversionMatrix = RGB_XYZ * XYZ_RGB;
+        Imath::M44f conversionMatrix = RGB_XYZ * XYZ_RGB;
 
-    unsigned char *img = new unsigned char[3 * w * h];
 
-    for (int y = 0; y < h; y++) {
-        for (int x = 0; x < w; x++) {
-            Imath::V3f rgb(pixels[y][x].r, pixels[y][x].g, pixels[y][x].b);
-            rgb *= conversionMatrix;
+        for (int y = 0; y < h; y++) {
+            for (int x = 0; x < w; x++) {
+                Imath::V3f rgb(pixels[y][x].r, pixels[y][x].g, pixels[y][x].b);
+                rgb *= conversionMatrix;
 
-            img[3*(y*w + x) + 0] =
-				(unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.x))));
-            img[3*(y*w + x) + 1] =
-				(unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.y))));
-            img[3*(y*w + x) + 2] =
-				(unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.z))));
+                img[3*(y*w + x) + 0] =
+                    (unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.x))));
+                img[3*(y*w + x) + 1] =
+                    (unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.y))));
+                img[3*(y*w + x) + 2] =
+                    (unsigned char)(255.0*std::min(1.0, std::max(0.0, to_sRGB(rgb.z))));
+            }
         }
+#ifdef USE_PREVIEW
     }
+#endif // USE_PREVIEW
 
     return img;
 }
@@ -103,5 +124,8 @@ extern "C" GdkPixbuf *file_to_pixbuf(const char *path, GError **error)
         free_buff,
         NULL);
 
+    // The pointer must remain valid,
+    // do not: `delete[] pixels;`
+
     return pixbuf;
 }