MagickSetImageCompressionQuality seems broken in 6.5.2
Posted: 2009-05-05T01:10:55-07:00
Hi,
I've recently ported an application that used the ImageMagick command-line tools to instead access the MagickWand API directly. Everything seems to be working well, except that the file size of the resulting JPEG images is considerably higher than when I was using the command-line tools. From some trouble-shooting, it seems that the call to MagickSetImageCompressionQuality() doesn't actually do anything--no matter what values I pass for 'quality', the resulting file size is the same. In case it's helpful, here is the order of the MagickWand API calls I'm using:
Any ideas? My only thought at the moment is that maybe there's something in the MagickGetImageBlob() code that isn't taking the quality setting into account.
I've recently ported an application that used the ImageMagick command-line tools to instead access the MagickWand API directly. Everything seems to be working well, except that the file size of the resulting JPEG images is considerably higher than when I was using the command-line tools. From some trouble-shooting, it seems that the call to MagickSetImageCompressionQuality() doesn't actually do anything--no matter what values I pass for 'quality', the resulting file size is the same. In case it's helpful, here is the order of the MagickWand API calls I'm using:
Code: Select all
wand = NewMagickWand ();
if (MagickReadImageBlob (wand, image, image_size)) {
// I cut out the non-IM stuff
if (!MagickCropImage (wand, width_cropped, height_cropped, x_offset, y_offset)) {
g_warning ("Couldn't crop image");
}
MagickResetImagePage(wand, NULL);
if (!MagickResizeImage (wand, width_scaled, height_scaled, SincFilter, 1)) {
g_warning ("Couldn't resize image");
}
MagickResetImagePage(wand, NULL);
MagickCropImage (wand, THUMB_WIDTH, THUMB_HEIGHT, x_offset, y_offset);
MagickNormalizeImage (wand);
MagickEnhanceImage (wand);
MagickSigmoidalContrastImage (wand, MagickTrue, 3.0, 60.0);
if (!MagickSetImageFormat (wand, "JPEG")) {
g_warning ("Couldn't set format to JPEG");
}
if (!MagickSetCompression (wand, JPEGCompression)) {
g_warning ("Couldn't set compression type");
}
if (!MagickSetCompressionQuality (wand, THUMB_QUALITY)) {
g_warning ("Couldn't set quality to %d", THUMB_QUALITY);
}
MagickStripImage (wand);
blob = MagickGetImageBlob (wand, &blob_size);
// Save the blob to glib-allocated memory
// so we can write all of the images to disk at once, later.
*thumbnail = g_new0 (gchar, blob_size);
memcpy (*thumbnail, blob, blob_size);
*thumbnail_size = blob_size;
MagickRelinquishMemory (blob);
}
}
DestroyMagickWand (wand);
