Use an explicit APNG identifier for apng files with ImageMagick

Required as per Imagemgick docs: https://imagemagick.org/script/formats.php

kittens/icat/magick.go

@@ -12,9 +12,9 @@ import (
 
 var _ = fmt.Print
 
-func Render(path string, ro *images.RenderOptions, frames []images.IdentifyRecord) (ans []*image_frame, err error) {
+func Render(path, original_file_path string, ro *images.RenderOptions, frames []images.IdentifyRecord) (ans []*image_frame, err error) {
 	ro.TempfilenameTemplate = shm_template
-	image_frames, filenames, err := images.RenderWithMagick(path, ro, frames)
+	image_frames, filenames, err := images.RenderWithMagick(path, original_file_path, ro, frames)
 	if err == nil {
 		ans = make([]*image_frame, len(image_frames))
 		for i, x := range image_frames {
@@ -41,7 +41,7 @@ func render_image_with_magick(imgd *image_data, src *opened_input) (err error) {
 	if err != nil {
 		return err
 	}
-	frames, err := images.IdentifyWithMagick(src.FileSystemName())
+	frames, err := images.IdentifyWithMagick(src.FileSystemName(), imgd.source_name)
 	if err != nil {
 		return err
 	}
@@ -56,7 +56,7 @@ func render_image_with_magick(imgd *image_data, src *opened_input) (err error) {
 	if scale_image(imgd) {
 		ro.ResizeTo.X, ro.ResizeTo.Y = imgd.canvas_width, imgd.canvas_height
 	}
-	imgd.frames, err = Render(src.FileSystemName(), &ro, frames)
+	imgd.frames, err = Render(src.FileSystemName(), imgd.source_name, &ro, frames)
 	if err != nil {
 		return err
 	}

tools/utils/images/loading.go

@@ -302,9 +302,13 @@ func check_resize(frame *ImageFrame, filename string) error {
 	}
 	expected_size := bytes_per_pixel * frame.Width * frame.Height
 	if sz < expected_size {
+		if bytes_per_pixel == 4 && sz == 3*frame.Width*frame.Height {
+			frame.Is_opaque = true
+			return nil
+		}
 		missing := expected_size - sz
 		if missing%(bytes_per_pixel*frame.Width) != 0 {
-			return fmt.Errorf("ImageMagick failed to resize correctly. It generated %d < %d of data (w=%d h=%d bpp=%d)", sz, expected_size, frame.Width, frame.Height, bytes_per_pixel)
+			return fmt.Errorf("ImageMagick failed to resize correctly. It generated %d < %d of data (w=%d h=%d bpp=%d frame-number: %d)", sz, expected_size, frame.Width, frame.Height, bytes_per_pixel, frame.Number)
 		}
 		frame.Height -= missing / (bytes_per_pixel * frame.Width)
 	}
@@ -439,11 +443,16 @@ func parse_identify_record(ans *IdentifyRecord, raw *IdentifyOutput) (err error)
 	return
 }
 
-func IdentifyWithMagick(path string) (ans []IdentifyRecord, err error) {
+func IdentifyWithMagick(path, original_file_path string) (ans []IdentifyRecord, err error) {
 	cmd := []string{"identify"}
 	q := `{"fmt":"%m","canvas":"%g","transparency":"%A","gap":"%T","index":"%p","size":"%wx%h",` +
 		`"dpi":"%xx%y","dispose":"%D","orientation":"%[EXIF:Orientation]"},`
-	cmd = append(cmd, "-format", q, "--", path)
+	ext := filepath.Ext(original_file_path)
+	ipath := path
+	if strings.ToLower(ext) == ".apng" {
+		ipath = "APNG:" + path
+	}
+	cmd = append(cmd, "-format", q, "--", ipath)
 	output, err := RunMagick(path, cmd)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to identify image at path: %s with error: %w", path, err)
@@ -476,10 +485,15 @@ type RenderOptions struct {
 	TempfilenameTemplate string
 }
 
-func RenderWithMagick(path string, ro *RenderOptions, frames []IdentifyRecord) (ans []*ImageFrame, fmap map[int]string, err error) {
+func RenderWithMagick(path, original_file_path string, ro *RenderOptions, frames []IdentifyRecord) (ans []*ImageFrame, fmap map[int]string, err error) {
 	cmd := []string{"convert"}
 	ans = make([]*ImageFrame, 0, len(frames))
 	fmap = make(map[int]string, len(frames))
+	ext := filepath.Ext(original_file_path)
+	ipath := path
+	if strings.ToLower(ext) == ".apng" {
+		ipath = "APNG:" + path
+	}
 
 	defer func() {
 		if err != nil {
@@ -500,7 +514,7 @@ func RenderWithMagick(path string, ro *RenderOptions, frames []IdentifyRecord) (
 	if ro.Flop {
 		cmd = append(cmd, "-flop")
 	}
-	cpath := path
+	cpath := ipath
 	if ro.OnlyFirstFrame {
 		cpath += "[0]"
 	}
@@ -621,11 +635,11 @@ func RenderWithMagick(path string, ro *RenderOptions, frames []IdentifyRecord) (
 }
 
 func OpenImageFromPathWithMagick(path string) (ans *ImageData, err error) {
-	identify_records, err := IdentifyWithMagick(path)
+	identify_records, err := IdentifyWithMagick(path, path)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to identify image at %#v with error: %w", path, err)
 	}
-	frames, filenames, err := RenderWithMagick(path, &RenderOptions{}, identify_records)
+	frames, filenames, err := RenderWithMagick(path, path, &RenderOptions{}, identify_records)
 	if err != nil {
 		return nil, fmt.Errorf("Failed to render image at %#v with error: %w", path, err)
 	}